As the name suggest this build is ALL about helping your team mates and restand heavy damage so that even IF something goes wrong you still have a pretty good chance of getting out of battle alive.

The Reason I go with "Strength of Spirit" instead of "Ardor" is that through out the build you will also get a bit extra mana you will also have a bit higher Hp regen per 5 sec through out the game.

As my and my team mates often goes for FB I pick Bandage toss as the first skill so that I can stun enemy champions and my friends will have an easier time killing him off.

The reason of max lv tantrum is that you deal a high ammount of magic damage + for each lv of Tantrum Amumu will recieve and reduced physical damage taking by 2 per lv. lv 5 tantrum = 10 less from physical damage per hit.

Then I go for Despair sinch it's a great Aoe damage that you can activate and use in EVERY situation. even if you are getting chased down you will still deal them a damage to take up the fight or giving your team mates easier time getting the Kill.

Sinch bandage toss already will provide the stun in lv 1 I wait to max this skill out last sinch it only provide stun and dmg to 1 enemy champion and no Aoe as Despair or extra Defence as Tantrum.

Marks : I have picked Greater Mark of Fortitude to Increase Amumu's Hp from early game on.

Seals : Greater Seal of Evasion is a great runes to give a tank cause it will give you a bigger chance to dogde enemy champion's attacks.

Glyphs : I have taking Greater Glyph of Warding to my tank because that Amumu's skill Tantrum will provide extra Armor in early game.

Quintessence : Greater Quintessence of Evasion is perfect for a tank and with this rune build you will get a dogde rating all up to 11.25 with is every 10 hit.

Doran shield is a good start item with extra Hp. extra Hp Reg and extra Armor. But elsway you should rush getting Glacial Shroud there will give you a good CD reduction for your ulti.

Remember that because of Amumu's skill Tantrum you will have an early advantage against physical damage dealing champions so you should go for magic resist first.

In late game I always end up selling Doran Shield and use the last slot to buy some sort of supporter Item according to which team mates you have

A few examples : If you got 2 physical focusing Ally Champion you should buy Stark's Fervor

If you got 2 Ability Power Focusing Ally Champion you should buy Abyssal
Scepter cause it will provide you with Magic Resist. Ap for your skills
Damage output and Reduced magic resistance for the enemy champions.

If you have to Ally there are taking lots af Damage Fast you should go for
Aegis of the Legion as it will provide with extra Armor & Magic resist to
your team mates and to yourself.

Use Bandage toss and tantrum combo a lot early game cause it will weaken your enemy's fast and give you an advantage + the Harrasment will often end up making your opponents do some few stupid mistakes there will provide you with easy kills.

Always be sure your team mates are near and prepared to attack when you go to Team Fights or use your Ulti (Curse of the sad mummy) sinch your the tank and They will deal the damage.

As all out tank don't be afraid of a death or 2 to save your friends it will pay out in late game.

In team fights Do everything you can to Harass your opponents so that they will target you instead of your team mates.