This build gives you the capability of being great help to your teammates while still giving you the chance to do well yourself. You will still be tanky, as Amumu should be, but you will be able to do good damage unlike a straight tank build.

-- Cursed Touch- This passive is great because the more basic attacking you do, the more vulnerable your target will be to your other abilities.

-- Bandage Toss- The pull and stun this offers is great for multiple scenarios. Be creative with it!
-Initiating an attack of any kind
-Catching up to a retreating enemy
-Stop enemies from attacking your teammates
-Getting through wall to escape (by attaching to a jungle monster)


-- Despair- This AOE is your best attack tool. Once you have this Maxed with a Sunfire Aegis and Abyssal Mask This is a GREAT tool. Your mere presence will hurt your enemies and if you stay on them long enough it will tear them up.

-- Tantrum Great for team fights because of how much you can spam it. This needs to be spammed and not forgotten about! In laneing phase this is a great tool for slowly tearing away enemy health.

-- Curse of the Sad Mummy- Fantastic for team fights! Instantly you can stop the entire enemy team for a few seconds which can turn the tides of the fight. you can also use it to stop enemies from escaping.

Not much to say here but there is one thing. Play around with how you upgrade Despair and Tantrum. Some games it is best to try maxing one all the way first then going for the other, while some games you may want to go back in forth. It is up to you. I personally always change the order i do it in.

Explanation of core items in order of acquisition:
-- Mercury's Treads- You are already a tank, lets make you more unstoppable by adding tenacity.

-- Sunfire Aegis- Amumu is 75% AOE so it would be in your best interest to make this AOE stronger. The Sunfire Aegis will passively add to your AOE and early game this is destructive.

-- Abyssal Mask- The Short range magic resist reduction will make Tantrum, Despair, and Curse of the Sad Mummy more powerful. This in combination with your basic attack Cursed Touch will make them extremely vulnerable.

-- Rylai's Crystal Scepter- The best of both worlds; you get both health and ability power. As a tanky AP type, this is perfect!

-- Archangel's Staff- This is a changeable item but for me I loved to bonus mana. Once it is upgraded you can leave Despair on and not have mana drained.