Welcome to my first Mobafire Build :)
At first i want to say, that im not english so pls dont complain about language errors.
This Build is about Amumu the said mummy.As i know most of the amumu players just see him as a pretty good tank and are not even a little bit aware of his absolutely overpowered Damage output.Because 2 of Amumus abilities stack 100% on Ap and one to 50%
i defenitely recommend playing him as an Ap-Tank.Not the way u maybe know it with all that rod of ages stuff but an other, new way.I hope u'll like it :)
LG Darkorbitmaster

+
-Amazing Ganker
-Huge Damage output
-Enemies wont expect you to deal this much Damage(Surprising effect)
-you can support as well(stun, mana, ...)
-pretty fast jungling
-very good survability even if you arent a tank(250 arour are pretty much, though)
-not dependent on kills, because nearly everitem is purchaseable
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-weak early game
-100% dead if ganked and not saved before the jungling starts(low movementspeed)
-high risk of being focused in teamfights
-a little dangerous to initiate into complete enemyteam(because of that I
buy the moonflair spellbalde)
-u will hear many complaining from your teammates calling you noob before
you actually show them what u can do with this way of building

Take Smite for succesfull jungling.Clarity is good for staying longer to Roam and ganking often and succesfully.Also you can help your teammates alot with your clarity mastery

i take 1/16/13 mastries, because we need the point in smite for the jungling
and the defensive points to withstand longer while jungling,too.The much Points in Utility are mostly because of the Exp and the Clarity mastery.

Take 9*mark of insight,9*dodging seals,9*manareg or healthreg glyphs and at least one Lifequint and 2 Ap Quints.(I know it sounds a little starnge, but believe me it works!)

Buy the cloth armour to withstand longer in jungle.Buy at least 3 if not 5 healthpots and star off with jungling.(description below).after your first basecall buy some normal boots and maybe a sightward wich you can place at dragon.then go on jungling and build the moonflair spellblade as fast as possible.try to gank whenever possible and remember your more a carry than a tank.though, you can Initiate pretty well with your ultimate.just try it and you will see it works out pretty well.So if you recall next time buy the sorcerers shoes and start building a thornmail.(depending on the situation you also can buil a Force of nature)after having completed this you buy sheen( no im not kidding : D )and after that the chainwest.Finish your lichbane emmidiately when you can do that.At this point you should start dealing most of the damage and making your enemies run.Just finish the guardian angel then, and take as your alst item Rabadons deathcap for even more heavy damage.(the many ap stack beautiful with your w; at the end of the game it has 4,7% of max.hp extra dmg -->ABsoltuely tanksmashing ;D)

Start off with the big Golem.Pop your w immediately and use the first potion when he lands his first hit.Just dps him down and smite him to death when he falls below 425 Hp.After having finished him off,toggle your despair off, go tho the wolves and kil the big one with w activated again.when he dies deactivate w immediatly. Use your second potion here.just go on killing the wraiths with w and spamming e,before you head over to the lizard camp.dont use a healthpotion if not absolutely necessary.spam e and w to lower him and kill him with your smite(when you arrive at him you should have around 16 secs cd on it).after that move on to the doublegolems kill them the same way and port back.just buy the items wich are listed and go into the jungle again. try to gank at this point and after your first gank go to lane and roam a lot.(use your clarity whenever you get low mana;dont think about the cooldown!!)

Many Amumu players say our q is made for initiating.Maybe they are right in some cases,but i recommend using it as a chasing ability,because of my damage based build.So go in pop your Ultimate when at least 3 Enemies are there and use yout tauntrum.Remeber to activating your aura all the time and grabbing the blue buff as often as possible because of that.Dont fall for traps,such as enemies luring you into grass and you toss in and stand in five enemies.not even your ulrimate saves you then.(remember you are no full tank!)So make sure you are alone or maximus against two.

It's really important to activate your Aura all the time! You dont belive what a incredible damage it deals.When you initiate( what your job as a Tank is), start off with bandage toss if there's no other way,then use your torment emmediatly and then just use it on cooldown. Dont use your toss as an opener when it isn't really of very big use , because it's really agood thing to chase enemys down.If you see a teamfight don't wait but just toss in Press r and try to kill the enemy tank (your aura will be very usefull, i promise ;) ).

I hope this build will be tested by many people, because it really works pretty well when not best ; ).
Please rate fair and think about it before you do.
Thank you
Greatings DO-Master