Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
in this build, i just would like to show you that Amumu is the most balanced tank.
With tantrum you have upped physical armor, then with your build you'll first up health then magic resist and finnally continue the up physical armor.
Personnally i always take forti while in premade. In pick-up you could pic, another one, i'll prefer teleportation ( if an enemy is attacking tower can be very usefull, tp -> ultimate -> bandage = no more creeps + tower attacking hero )
Clarity is a must have, if you're lacking mana for bandage, or despair...
As i said, amumu is very balanced, so i personnally take runes for magic, physical resistance and health. He can be build on dodge too, coupled with Ninja tabi.
I just specify that certain items will depend of the team infront of you :
Ninja Tabi instead of Mercury Treads
If more physical heroes of if you see that magical ones won't be a major problem.
Leviathan must be taken early in the game, if not go for warmog.
Guardian angel can be replace by force of the nature depending on how dangerous is the team infront of you.
Lately in the game we could sell chalice for Aegis : aura + armor + health
Bandage Toss : I think it's a good idea to take it as first skill, coupled with a heroe with some C/C can be very efficient.
Despair : Must be used with precaution, it will drain your mana very fast, try to get golem aura to prevent it. But very nice againt maxxed health tanks, with a sunfire cape, it will be even better.
Tantrum : For me, best skill from amumu, it passively increase physical armor, and actively great for farming and killing fast. Try to pack minions if you want tantrum to be very effective.
Curse of the Sad Mummy: What about this one... the best skill for AoE team's, the largest CC skill. Use it nicely, the cooldown is pretty long. But a well placed Curse of the Sad Mummy will set up the fate of enemies.
Early in the game, just farm.. if your lane's ally is reactive you can try the FK :)
In the middle of the game, i'll advise to continue farming but as you're a great "fight initiator", you will be the master piece of the team.
In a late game, if your build is almost up, you should be nearly unkillable even more if your leviathan is fully stacked.
Amumu is a verry effective tank, for me the most balanced. So use him :)
If there is any question or comment don't hesitate, i'm open to any constructive critique
ps : sorry for my bad english