I've been playing Nasus a lot lately and i've also been seeing a lot of people play Nasus, but most of the Nasuses i see are frankly not that great. Yeah, they often get the job done... but i think there's a better way of doing things.
That said, i'm not some expert myself. I'm still learning, so this will probably look pretty silly when everyone has more experience. But i think it works now.
(* Note: If you're wondering why i called him a librarian in the thread title: go read his lore!)
Meta-Info
Note that this guide is written for the 10/21/09 patch. Future patches may render it obsolete.
First i'm going to explain what you will do as Nasus, then i am going to explain the choices you will make to build him. I think this is a more reasonable way of talking about this champion: once you see how he should play the items you get should be more sensible. Note that this also all applies to Summoner's Rift. If you are playing on Twisted Treeline things are quite different and i think Nasus actually loses a little bit of his power.
Early Game (Pre-laning)
Depending on what you are doing you will want to pick a different skill. If you're going straight into a lane you might want your Siphoning Strike, to start getting damage. If you're going to gank or creepjack you might want Wither to slow. If you're going to do some jungle creeps or level 1 dragon or if you know you're getting into a team fight you might want to take Spirit Fire. Which one you get is a matter of your strategic advantages. You will need to exercise your personal judgment on a per-game basis.
You should also try to secure solo mid lane for yourself. You can lane with a partner, though that partner may end up not getting many creep kills, or you can lane somewhere other than mid (but be more vulnerable to ganks) but you are best at solo mid.
Early Game (Laning)
Start out either by last hitting (with Siphoning Strike if you have it) or throwing Spirit Fire down and then stealing creep kills. At low levels, Spirit Fire will not do that much damage. However, level it up and it will soon be able to kill an entire wave of creeps in a single cast--which also makes for easy Siphoning Strike last hits!
Early-Mid Game (Laning, Ganks, Skirmishes)
This is somewhat an awkward time for Nasus. The kind of fights you're really good at are probably not happening yet, and even if they are your gear may not be good enough (yet) to make you strong enough to matter. On the other hand, your team will probably be running around and getting into small fights and you will want to contribute. (Wither is the key, here.) But at the same time you naturally will want to remain farming as long as you possibly can, because your laning gold will be your biggest single gain throughout the entire game. in addition, it's very hard for the enemies to out-lane you (Teemo can do it, but i haven't run into anyone else who can beat you without a player skill advantage.).
That said, like when gambling, you need to know when to put the laning game down and transition into something else. This is another personal judgment thing, but if you do it too soon you will not have enough gold later on and if you do it too late your team will already be far behind by the time you start joining them. Although you are a big presence in fights, you cannot carry your team. You are a tank, with a big of support/DPS enhancement, and your natural habitat will eventually become team fights. In my opinion you should shoot for between 100 and 200 creep kills at around this point. Maybe a little less if you are just starting to learn Nasus.
Mid Game (Skirmishes, Team Fights, Ganks, More Laning, Tower Pushes)
This is when you start getting exciting again. Once you get geared up you will become quite powerful and durable, so your team will want to begin getting into team fights with you as a main tank or off tank. In skirmishes you can hit your ult and then (with luck) get a kill or two, putting your team at an advantage. You can get neutral creeps quite effectively (though you don't have much use for the buffs) and can even solo dragon (though it takes a while--just make sure you're not abandoning your team).
Ultimately, unless you ace the enemy team through luck or something, your items and such will not be enough to end the game at this point. Your power will probably apex around here, so you will begin to take a more supportive role as the game continues. With your ult up you can still do tons of damage in team fights (increasing all the time, most likely) and you become a dangerous chaser with Wither.
Late Game (Baron, Inhibitors, Game Ending Fights)
Eventually characters will become strong enough that they can handle you without too much trouble again. Carries will be able to cut you down quickly, support characters will be able to disable you for a dozen seconds at a time, and tanks (although they will take quite a lot of damage from your ult) will be able to ignore you to an extent.
At this stage your presence becomes more tactical.
Spirit Fire when the battle is static (so the enemies will have to surrender advantageous terrain or fight in Spirit Fire).
Wither a key enemy champion when the battle is dynamic, or (more importantly) when the enemies are in a disadvantageous position. This will require them to fight when they didn't want to.
Use Siphoning Strike to add damage to key targets.
Your ult should either be used to initiate (make them waste disables on you) or to deal damage during team fights. It can also be used in desperate situations, possibly when the enemies are hoping to quickly kill one or more of your allies and then clean up or escape. It can quickly change the "math" of a battle back into your favor if the enemies over-extend or take risks.
You can use Rally during pushes to add damage to towers, during team fights to help your team survive and increase the strength of your team's physical DPS (as long as the enemies don't just retreat away from the aura), or (most importantly) during decisive battles you can turn a victory into a rout and turn what was going to be a small advantage into a large one.
A well-timed use of Wither, Spirit Fire, Fury of the Sands, and Rally can win the game. You may not be the team carry, but you can be its leader--direct the team, lead them into battle, enable your allies, and keep people focused. This is somewhat dependent on the player, though--if you don't have the right skills for leadership yourself you might want to let someone else lead your team. (Of course on the other hand... you can get those skill by practicing them!)
Anyway, that's what you should do during the various stages of the game. Or at least, that's what i think you should do
Next i'm going to give a brief overview of different situations you will find yourself in:
Laning
If the enemies have strong harassment you will want to give them room. Try to keep your Spirit Fire in between yourself and your enemies. Let Spirit Fire farm (delay your cast slightly so your creeps will damage the enemy creeps, then you can cast it and hopefully still get last hits). If ganked, Wither on a dangerous foe and flee. Even with assistance you will probably lose a gank--avoidance is key, here. If you are desperate, and if you will not need it soon, you can drop your Rally while you run to try recovering HP enough to escape. Very few champions can beat your combination of farming, self-healing (with lifesteal on your physical damage) and safety.
Ganking
Wither is the key here. If your allies have "skillshot" disables you should lead with Wither to let them land their disables more easily. Otherwise, cast Spirit Fire a little before the end of the previous disable to bring the slow up faster. Holding the target still while you focus fire is key! Use Spirit Fire and Siphoning Strike to deal damage and enhance the damage of your allies. Generally it is not worth using your ult to kill one target--if your fortunes change you should run rather than turn your ultimate on and try to fight.
Skirmishes/Creep-jacking/Etc
Generally what will happen is you will stumble on the enemies, or they will stumble on you, or you will try to jump them while they are dragoning, or something along those lines. You need to use your judgment here. Sometimes it will be worth using your ultimate, sometimes not. Consider the situation--is one of your team being ganked? How badly do you want to save that person? Are you willing to die so they can live? That's not a rhetorical question, by the way--you can die, although dying early is bad, and you can often soak quite a bit of punishment... so if it will save an important ally or multiple allies you may want to just turn your ultimate on and rush the enemies, forcing them to deal with you instead of your friends.
Team Fights
It's hard to give any definite advice for team fights, as they are the most complicated part of the game. Generally things happen in this order:
Incidentally, i hate to keep mentioning suiciding onto the other team. You should really do it very rarely--maybe once a game, maybe less, and always as little as you possibly can. But you can soak quite a lot of punishment and you aren't relying on champion kills to get powerful, so it's better you than (say) your team carry.
So that's a big overview of what Nasus does. How do we get there from here?
Masteries
You can go 21/0/9, 0/21/9, or 9/0/21. (Or 0/9/21, for that matter.) Which isn't really surprising--specialize in offense, defense, or utility? Generally your preference will be Utility, Defense, then Offense as your main. Note that all of these builds take at least 8 (technically at least 9) points in Utility, as this is important.
Awareness may not seem like such a big deal, but it is. Awareness means that if you and your lane opponent sit in lane and do nothing you will be higher level. Since you farm like crazy you will have more gold. Unless the other team has Zilean or something crazy like that you should be at least equal, and maybe higher, level than their solo and you should have more gold. You don't have to get kills to do this, you don't have to really put yourself at too much risk, you just have to sit around and Spirit Fire on all six creeps. Your goal should be safety and efficiency. This way you don't have to make big, decisive plays to get an advantage, you can let the game mechanics work things out in your favor.
Summoner Spells
Generally i am assuming you take Rally. You can not take Rally (especially if an ally has Rally--you probably don't want two, but you could get two in some situations) and instead take another spell (Clairvoyance, Fortitude, Heal) but Rally will (i believe) give you the biggest boost throughout the game.
For your second spell you are probably taking Teleport. That's super-lazy, but you want to not be on the other side of the map when your team wants to do something and you want to not spend a lot of time moving between lanes when shopping or what have you. The less time you're out of lane, the more you can take advantage of your natural farming and (with Awareness) experience gain. The other prime candidate, though, is Ghost. This lets you use your ultimate better, and so on. Ghost also helps you escape from ganks, which is relevant.
I know this is going to make some people unhappy--specifically i'm talking about the people who think running 5x Flash/Teleport on every team is the best way to go--but i think it's right for Nasus. Flash is (of course) quite good, but it's not really a good match to Nasus.
Runes
To be honest, i'm not entirely sure anymore. I'll go over some theoretical ideas:
Marks
You're not going to critical, or really auto-attack much at all, so the DPS runes aren't that great. Armor penetration is attractive, but not very useful. (It doesn't help you last hit creeps at all.) You might want spell penetration, now that you can get it on marks, but on the other hand you might just want to get HP.
Seals
You will probably want HP (in some form) or evasion. Getting armor or magic resist (depending on the kind of team you're expecting) is also reasonable.
Glyphs
Getting mana regeneration is always attractive, though getting cooldowns is also nice. Consider taking some magic resist.
Quintessences
Movespeed is probably the best here. Your other options include flat +HP (helps laning) or, if you're being very sneaking, getting the +2% experience earned runes. Those will help you get more out of your laning plan, although once you hit level 18 their advantage begins decreasing until you are worse off overall than if you had gone some other runes.
Items
Finally, an item build. This is my suggestion. If i feel like it, i may come back and elaborate on items you don't want to take (but which you might think you do).
Start with a Meki Pendant and two healing potions. This will help you spam Spirit Fire in lane. (If you don't feel the need for more mana than that--say you have mana regen runes and masteries--then start with a Doran's Ring as it is even better. It will let you kill the ranged creeps with Spirit Fire at level 2, instead of 3.)
You'll probably want boots next, though you can hold off on upgrading them. The only two you want to consider are Boots of Swiftness or Mercury's Treads. Mercs make you much harder to kill or lock down, which is good. (And don't just think of yourself here--the more spells they have to pump into you the fewer they are pumping into your teammates!)
You can upgrade the Meki Pendant into something--probably a Chalice--for additional boosts. Chalice's mana regen is very strong, and the magic resist is usually a great stat.
From there you have some choices. Generally an Aegis is a good buy, so consider that. After that (or if someone else has an Aegis) consider Stark's Fervor. That gives you additional lifesteal (which is nice), attack speed, etc, and the armor reduction stacks with Spirit Fire. This will help you send enemy armor values down into levels where they will take lots of damage--especially if you have additional armor reduction on your team. If you already have Aegis and Stark's (on you or someone else) then consider getting some Sunfire Capes. These are great against physical damage, and help you do more damage while you're running up alongside people with your ultimate on.
Other than that items are pretty much situational. You can get a Frozen Heart for physical teams, Banshee's Veil for magical teams (even though you don't really need the spell block), Warmog's, Mallet, Elixir of Fortitude, whatever.
As an alternate opening item build, if you know the game is going long, you can get a Philosopher's Stone and then a Heart of Gold or two. Remember you don't want to sell any of this stuff until around 20 minutes after you bought it, and ideally even later than that. (Don't put off buying items, of course!) You should be able to quickly farm them up, and this way you can keep getting gold after the laning phase.
Whew.
Well, that's all for now. I'll probably take a nap and then come back and edit this for typos and the like.
That said, i'm not some expert myself. I'm still learning, so this will probably look pretty silly when everyone has more experience. But i think it works now.
(* Note: If you're wondering why i called him a librarian in the thread title: go read his lore!)
Meta-Info
Note that this guide is written for the 10/21/09 patch. Future patches may render it obsolete.
First i'm going to explain what you will do as Nasus, then i am going to explain the choices you will make to build him. I think this is a more reasonable way of talking about this champion: once you see how he should play the items you get should be more sensible. Note that this also all applies to Summoner's Rift. If you are playing on Twisted Treeline things are quite different and i think Nasus actually loses a little bit of his power.
Early Game (Pre-laning)
Depending on what you are doing you will want to pick a different skill. If you're going straight into a lane you might want your Siphoning Strike, to start getting damage. If you're going to gank or creepjack you might want Wither to slow. If you're going to do some jungle creeps or level 1 dragon or if you know you're getting into a team fight you might want to take Spirit Fire. Which one you get is a matter of your strategic advantages. You will need to exercise your personal judgment on a per-game basis.
You should also try to secure solo mid lane for yourself. You can lane with a partner, though that partner may end up not getting many creep kills, or you can lane somewhere other than mid (but be more vulnerable to ganks) but you are best at solo mid.
Early Game (Laning)
Start out either by last hitting (with Siphoning Strike if you have it) or throwing Spirit Fire down and then stealing creep kills. At low levels, Spirit Fire will not do that much damage. However, level it up and it will soon be able to kill an entire wave of creeps in a single cast--which also makes for easy Siphoning Strike last hits!
Early-Mid Game (Laning, Ganks, Skirmishes)
This is somewhat an awkward time for Nasus. The kind of fights you're really good at are probably not happening yet, and even if they are your gear may not be good enough (yet) to make you strong enough to matter. On the other hand, your team will probably be running around and getting into small fights and you will want to contribute. (Wither is the key, here.) But at the same time you naturally will want to remain farming as long as you possibly can, because your laning gold will be your biggest single gain throughout the entire game. in addition, it's very hard for the enemies to out-lane you (Teemo can do it, but i haven't run into anyone else who can beat you without a player skill advantage.).
That said, like when gambling, you need to know when to put the laning game down and transition into something else. This is another personal judgment thing, but if you do it too soon you will not have enough gold later on and if you do it too late your team will already be far behind by the time you start joining them. Although you are a big presence in fights, you cannot carry your team. You are a tank, with a big of support/DPS enhancement, and your natural habitat will eventually become team fights. In my opinion you should shoot for between 100 and 200 creep kills at around this point. Maybe a little less if you are just starting to learn Nasus.
Mid Game (Skirmishes, Team Fights, Ganks, More Laning, Tower Pushes)
This is when you start getting exciting again. Once you get geared up you will become quite powerful and durable, so your team will want to begin getting into team fights with you as a main tank or off tank. In skirmishes you can hit your ult and then (with luck) get a kill or two, putting your team at an advantage. You can get neutral creeps quite effectively (though you don't have much use for the buffs) and can even solo dragon (though it takes a while--just make sure you're not abandoning your team).
Ultimately, unless you ace the enemy team through luck or something, your items and such will not be enough to end the game at this point. Your power will probably apex around here, so you will begin to take a more supportive role as the game continues. With your ult up you can still do tons of damage in team fights (increasing all the time, most likely) and you become a dangerous chaser with Wither.
Late Game (Baron, Inhibitors, Game Ending Fights)
Eventually characters will become strong enough that they can handle you without too much trouble again. Carries will be able to cut you down quickly, support characters will be able to disable you for a dozen seconds at a time, and tanks (although they will take quite a lot of damage from your ult) will be able to ignore you to an extent.
At this stage your presence becomes more tactical.
Spirit Fire when the battle is static (so the enemies will have to surrender advantageous terrain or fight in Spirit Fire).
Wither a key enemy champion when the battle is dynamic, or (more importantly) when the enemies are in a disadvantageous position. This will require them to fight when they didn't want to.
Use Siphoning Strike to add damage to key targets.
Your ult should either be used to initiate (make them waste disables on you) or to deal damage during team fights. It can also be used in desperate situations, possibly when the enemies are hoping to quickly kill one or more of your allies and then clean up or escape. It can quickly change the "math" of a battle back into your favor if the enemies over-extend or take risks.
You can use Rally during pushes to add damage to towers, during team fights to help your team survive and increase the strength of your team's physical DPS (as long as the enemies don't just retreat away from the aura), or (most importantly) during decisive battles you can turn a victory into a rout and turn what was going to be a small advantage into a large one.
A well-timed use of Wither, Spirit Fire, Fury of the Sands, and Rally can win the game. You may not be the team carry, but you can be its leader--direct the team, lead them into battle, enable your allies, and keep people focused. This is somewhat dependent on the player, though--if you don't have the right skills for leadership yourself you might want to let someone else lead your team. (Of course on the other hand... you can get those skill by practicing them!)
Anyway, that's what you should do during the various stages of the game. Or at least, that's what i think you should do
Next i'm going to give a brief overview of different situations you will find yourself in:
Laning
If the enemies have strong harassment you will want to give them room. Try to keep your Spirit Fire in between yourself and your enemies. Let Spirit Fire farm (delay your cast slightly so your creeps will damage the enemy creeps, then you can cast it and hopefully still get last hits). If ganked, Wither on a dangerous foe and flee. Even with assistance you will probably lose a gank--avoidance is key, here. If you are desperate, and if you will not need it soon, you can drop your Rally while you run to try recovering HP enough to escape. Very few champions can beat your combination of farming, self-healing (with lifesteal on your physical damage) and safety.
Ganking
Wither is the key here. If your allies have "skillshot" disables you should lead with Wither to let them land their disables more easily. Otherwise, cast Spirit Fire a little before the end of the previous disable to bring the slow up faster. Holding the target still while you focus fire is key! Use Spirit Fire and Siphoning Strike to deal damage and enhance the damage of your allies. Generally it is not worth using your ult to kill one target--if your fortunes change you should run rather than turn your ultimate on and try to fight.
Skirmishes/Creep-jacking/Etc
Generally what will happen is you will stumble on the enemies, or they will stumble on you, or you will try to jump them while they are dragoning, or something along those lines. You need to use your judgment here. Sometimes it will be worth using your ultimate, sometimes not. Consider the situation--is one of your team being ganked? How badly do you want to save that person? Are you willing to die so they can live? That's not a rhetorical question, by the way--you can die, although dying early is bad, and you can often soak quite a bit of punishment... so if it will save an important ally or multiple allies you may want to just turn your ultimate on and rush the enemies, forcing them to deal with you instead of your friends.
Team Fights
It's hard to give any definite advice for team fights, as they are the most complicated part of the game. Generally things happen in this order:
- Initiation: Either one team will begin spending abilities in order to initiate on the other (believing they have an advantage in overall power if the fight happens, even if they have to put themselves at a disadvantage by making the first move) or one team will make a mistake and get caught out of position. You could be involved in the first (using Wither and your ultimate to initiate), but you don't want to be a part of the second and--if necessary--you should direct your teammates so everyone can be safe. You should have a team fight advantage (unless your team composition is poor--if you have Nasus you want a team that can do team fights), so the first scenario is good whereas taking risks (and maybe ending up on the receiving end of the second) is very bad because it would give up Nasus's big advantage. You took your risks up front (by picking Nasus and aiming at team fight superiority), so don't risk getting stupidly killed and having your advantage neutralized.
- Initial clash: Spells will go off, teams will begin dealing damage, and at some point one team will realize they are losing. A champion (or more than one) may be killed.
- Regrouping and re-evaluating: If the results were pretty even the teams will probably back off, wounded. At this point there may still be fighting, but everyone is trying to stabilize the situation. If your ultimate is down and your team doesn't have any other tricks up its sleeve you might want to retreat in an orderly fashion. (This might involve sacrificing you or another champion, which is not what you want to do but it's better than getting aced.) If the battle lines shift you want to Wither someone.
- Chasing and taking advantage of the situation: If your team got an advantage you will want to press in now. If you got some kills, but are not strong enough to kill buildings, you may want to go kill the biggest neutral creep your team can safely kill. If you can get a building do it now. If you can chase and get additional kills do that. Basically whatever sort of advantage you can get, you should take. If you are losing then this stage is not where you want to be--you need to quickly determine what the least bad outcome is and shoot for that. This is not the time for Nasus to be the hero, unless it's by sacrificing himself.
Incidentally, i hate to keep mentioning suiciding onto the other team. You should really do it very rarely--maybe once a game, maybe less, and always as little as you possibly can. But you can soak quite a lot of punishment and you aren't relying on champion kills to get powerful, so it's better you than (say) your team carry.
So that's a big overview of what Nasus does. How do we get there from here?
Masteries
You can go 21/0/9, 0/21/9, or 9/0/21. (Or 0/9/21, for that matter.) Which isn't really surprising--specialize in offense, defense, or utility? Generally your preference will be Utility, Defense, then Offense as your main. Note that all of these builds take at least 8 (technically at least 9) points in Utility, as this is important.
- Offense has some good stuff in it, including additional damage and cooldowns. Note that if your team has lots of spell damage you can also take Rally Mastery here. (Rally Mastery is probably the biggest reason to take Offense to 21.) You, yourself, don't benefit from Rally Mastery that much, though, and your supporting ability is primarily supporting physical DPS so this is not that exciting. You can get additional damage to enhance your Siphoning Strike last hitting, here.
- Defense makes you tougher, which is always good as you are a tank. If you want to get Fortify you can take Fortify Mastery and get easier last hits (which helps you improve Siphoning Strike).
- Utility gives you a lot of stuff you really want: Good Hands (death reduction), move speed increase (good for your ult), reduced cooldowns (especially if you 9/0/21), reduced summoner spell cooldowns (good for Rally's gigantic cooldown), and most importantly of all, Awareness (that is: the +5% experience rate mastery).
Awareness may not seem like such a big deal, but it is. Awareness means that if you and your lane opponent sit in lane and do nothing you will be higher level. Since you farm like crazy you will have more gold. Unless the other team has Zilean or something crazy like that you should be at least equal, and maybe higher, level than their solo and you should have more gold. You don't have to get kills to do this, you don't have to really put yourself at too much risk, you just have to sit around and Spirit Fire on all six creeps. Your goal should be safety and efficiency. This way you don't have to make big, decisive plays to get an advantage, you can let the game mechanics work things out in your favor.
Summoner Spells
Generally i am assuming you take Rally. You can not take Rally (especially if an ally has Rally--you probably don't want two, but you could get two in some situations) and instead take another spell (Clairvoyance, Fortitude, Heal) but Rally will (i believe) give you the biggest boost throughout the game.
For your second spell you are probably taking Teleport. That's super-lazy, but you want to not be on the other side of the map when your team wants to do something and you want to not spend a lot of time moving between lanes when shopping or what have you. The less time you're out of lane, the more you can take advantage of your natural farming and (with Awareness) experience gain. The other prime candidate, though, is Ghost. This lets you use your ultimate better, and so on. Ghost also helps you escape from ganks, which is relevant.
I know this is going to make some people unhappy--specifically i'm talking about the people who think running 5x Flash/Teleport on every team is the best way to go--but i think it's right for Nasus. Flash is (of course) quite good, but it's not really a good match to Nasus.
Runes
To be honest, i'm not entirely sure anymore. I'll go over some theoretical ideas:
Marks
You're not going to critical, or really auto-attack much at all, so the DPS runes aren't that great. Armor penetration is attractive, but not very useful. (It doesn't help you last hit creeps at all.) You might want spell penetration, now that you can get it on marks, but on the other hand you might just want to get HP.
Seals
You will probably want HP (in some form) or evasion. Getting armor or magic resist (depending on the kind of team you're expecting) is also reasonable.
Glyphs
Getting mana regeneration is always attractive, though getting cooldowns is also nice. Consider taking some magic resist.
Quintessences
Movespeed is probably the best here. Your other options include flat +HP (helps laning) or, if you're being very sneaking, getting the +2% experience earned runes. Those will help you get more out of your laning plan, although once you hit level 18 their advantage begins decreasing until you are worse off overall than if you had gone some other runes.
Items
Finally, an item build. This is my suggestion. If i feel like it, i may come back and elaborate on items you don't want to take (but which you might think you do).
Start with a Meki Pendant and two healing potions. This will help you spam Spirit Fire in lane. (If you don't feel the need for more mana than that--say you have mana regen runes and masteries--then start with a Doran's Ring as it is even better. It will let you kill the ranged creeps with Spirit Fire at level 2, instead of 3.)
You'll probably want boots next, though you can hold off on upgrading them. The only two you want to consider are Boots of Swiftness or Mercury's Treads. Mercs make you much harder to kill or lock down, which is good. (And don't just think of yourself here--the more spells they have to pump into you the fewer they are pumping into your teammates!)
You can upgrade the Meki Pendant into something--probably a Chalice--for additional boosts. Chalice's mana regen is very strong, and the magic resist is usually a great stat.
From there you have some choices. Generally an Aegis is a good buy, so consider that. After that (or if someone else has an Aegis) consider Stark's Fervor. That gives you additional lifesteal (which is nice), attack speed, etc, and the armor reduction stacks with Spirit Fire. This will help you send enemy armor values down into levels where they will take lots of damage--especially if you have additional armor reduction on your team. If you already have Aegis and Stark's (on you or someone else) then consider getting some Sunfire Capes. These are great against physical damage, and help you do more damage while you're running up alongside people with your ultimate on.
Other than that items are pretty much situational. You can get a Frozen Heart for physical teams, Banshee's Veil for magical teams (even though you don't really need the spell block), Warmog's, Mallet, Elixir of Fortitude, whatever.
As an alternate opening item build, if you know the game is going long, you can get a Philosopher's Stone and then a Heart of Gold or two. Remember you don't want to sell any of this stuff until around 20 minutes after you bought it, and ideally even later than that. (Don't put off buying items, of course!) You should be able to quickly farm them up, and this way you can keep getting gold after the laning phase.
Whew.
Well, that's all for now. I'll probably take a nap and then come back and edit this for typos and the like.
