*Please read all guide in order to vote for it, and if you are going to vote -1, please leave the reason in a comment, and i'll read it and consider it, because I'm not a Pro player, and i just wanted to make a guide because i tried and liked this build. Any comments that can help improve this guide will be added, and credit given to the user. If you were expecting a full tank guide (and then a boring Amumu playstyle IMO), you can consider to GTFO! :) *

(My main language isn't english, sorry for the mistakes, thx).

Amumu guide!, i started to play it and i loved it, but the only bad thing is the early game, because Amumu is easily pushed out of the minions. So you need a good lane partner, somebody with range (I prefer a dps one, because the enemy champs can't build armor for both of u easily, and normally they build mercury threads, so dps will be happy)

*THIS BUILD WASN'T TESTED MANY TIMES (20-), SO I WILL TRY TO IMPROVE IT IN TIME :)*

*As the title says, this is an AP/Offtank guide, so it's more AP than offtank. This guide is focused on dealing a LOT of damage to enemy tanks ( Despair) and a decent amount to other types ( Bandage Toss + Tantrum)*

Pros:

-Almost all skills are AoE, so u will get a lot of gold from assists, a LOT.
-Not a normal gank target.
-Good ganker because of ur toss and ultimate.
-Can jungle too, but this is a lane guide c:
-Mana is running out? in mid-late game there's always a blue buff to help :) (You need to ward it)
-Pro of this build comes in late game, if u feel that you cant last as a tank, rush the will of the ancients (reasons, later).

Cons:
-Early game sucks
-Maybe not a lot item dependant, but team dependant.
-Mana runs out really fast. (No Chalice of Harmony in this build)
-Not a OMGWTF burst damage (decent....ok, low.), and the DoT that does needs close range.
-Not many ways to get into the fight (only toss and summoner spells like Flash, Ghost

Not many things to explain here, runes will help in ealry game for the mp5, and to do more damage, heal yourself more (*), and more mobility (very needed in Amumu).

*As bigfatcow says, this build covers DPS incoming damage, but it have low Mresistance to be a tank (btw this was planned to be an offtank guide), so you can replace the celerity glyphs with glyphs of shielding, that gives almost 3 mres per rune.

-Or, you can do a hybrid-type and put 3 shielding (To get near 120 mres) and 6 celerity, or 6 shielding for 130mres and 3 celerity, you choose :)

Testing masteries too, any suggestions for the masteries that would fit to this build will be considered.
I think 9/21/0 is good, becuase of the MPen, and def to last more.

¿Why not 0/21/9 for Amumu? ¿Isn't Runic Affinity good for Amumu since you said mana issues were not a problem with buff? Not in this build, because of Will of the ancients. Not a very used item, but it gives a nice 25% spell vamp AURA. More enemies in AoE range? more heal for yourself (I've seen like 100+ hp per sec with 3 champs (1 tank) in Despair's range.)
And about mana.... in higher lvls (15+) u wont have mana problems, just enough for a big teamfight and survive.

So that 9 in offense will help you last long in team battles.

Item section!! :D

Well, normally start with a Regrowth Pendant and a Mana Potion. That will give enough durability to get money in your first trip to base, and buy Philosopher's Stone (nice regen and GP5!!! just what we need) and Boots (and 1-2 mana potions if u can afford it).

With that, you can farm and push till mid-game. (Yeah, push, you aren't going to kill everyone, just push and get assists in early-mid)


-Now, core items!!! :D

Well, this is a bit hard to pick. If your second trip to base was a bit too early, that's because you need more health and survability. BUILD Sunfire Aegis ASAP!
If that wasnt the case, and you had enough time to get a nice amount of gold, you need to build your bomb (AP). I'm not sure if Rylai's Crystal Scepter or Abyssal Mask, or Hextech Revolver....

-Things you can see for chosing right:
¿Your lane partner have CC and can heal (like Taric, even if he's not ranged)? Build Abyssal Mask.
¿Your lane partner hace CC? Build Hextech Revolver, cheap and good spellvamp.
¿Your lane partner doesn't have CC? / ¿You want to have more health and you have a lot of gold? Build Rylai's Crystal Scepter.

But! IMO is better to build Hextech Revolver first, then Rylai's Crystal Scepter, then Sunfire Aegis.
(Don't forget to upgrade your boots to Mercury's Treads, do it first than core items if the enemy team have a lot of cc's)

* With this core build, you can go to find friends with Amumu, and hug 'em :) *

Now that you have those items, comes more questions:

-'I can't stay in a teamfight, we win/lose but i always die': Upgrade to.... Will of the Ancients!!! Yeh, i know, normally Amumu is the tank, need health and ressistances, so why not a Warmog, or more armor if they are dps, or Mresist if they are ap...? Because! this build isnt 100% tank, and Will of the Ancients fits PERFECTLY with your skills. Underrated item that gives you a nice amount of AP and Spellvamp aura. Your AP carries will be happy, and you too. With maxed despair you can heal great amounts, and only for 8mpsec.

-We have a healer, like Soraka, but our team don't deal 'tons of damage' and teamfights are lasting a lot./ Their team have AP carry that is pwning us all : This means you need to build Abyssal Mask!! Close range, 1 auto-attack and let your AoE and passive do the rest. And nice mresist.

-Their team have a DPS carry feeded D:!!!! / Cooldowns sux ¬¬ : Frozen Heart. Nothing more to say. GOOD armor bonus, GOOD CDR, slows aspd of carries!! :D all in one, now Amumu isn't so sad.

And obviously you need to sell the Philosopher's stone in order to get your 6th item, but your final build should look like this:

Mercury's Treads
Rylai's Crystal Scepter
Sunfire Aegis
Will of the Ancients
Abyssal Mask
Frozen Heart

You can choose the order by this guide, or by looking how the match is going.
(You can also change Frozen Heart into Thornmail if you want to punish their dps, but that's a tank build already, so go look other guide ^^)

The moment has come.

IMO, mobility is the best choice for Amumu, so i would pick Flash or Ghost for that... or both....

BUT! you always have to think about cc's, and even with mercury threads, a well placed CC in a bad place for you can get you down. So Cleanse is a good option too. This spell used in the right time will save you, never gonna give u up, and never gonna let you down :) (Lol)

Normally i would pick Cleanse and Ghost, some people think Flash is better than Ghost? Pick flash instead. Cleanse sux? pick Flash/Ghost then, is your game, not mine :) play ir as you want. I'm just trying to help, not saying what do u HAVE to do.

Teamwork, the best that Amumu can do! So you need a partner first (In most games, Ashe seems to make a good team with this [[Amumu build...) or two... or all your team! just with 1 partner you can kill/assist, and the enemy team will fear you in close range. Oh! but we can get in range easily >:D a well placed Bandage Toss = You have slain an enemy.

Now, about teamwork. ALWAYS try to use your Curse of the Sad Mummy when blue buff is active, because cooldown is HUGE! And, have a bit of common sense and dont use ur ulti for 1 enemy champ. Omg really? I put this here because i've seen some Amumus using Ulti to get 1 enemy down......... rare cases, but it happens.

2 champs? ult's not necessary, but if you can do it, your warded jungle says no probable gank for you or your teammate? go for it :)

Teamfight? 5 Enemies? TOSS to the middle, but aim to a champ (please), and use Curse of the Sad Mummy when they have ABOUT HALF hp, because that will stop em all, let your teammates do more damage, and that will result to a flee of the enemy team, and 3-4-5 kills, and obviously, 5 assists (or kills...) for you, and the gold... the GOOOOLD *-*

Skills!

Your passive Cursed Touch is a bomb, like Abyssal Mask, but free. It reduces the mresist of a target you autoattacked for a time. Try always to autoattack the target you are chasing.

Your Q is Bandage Toss, the enemy's second nightmare. Gets you in range, and stuns. Avg cooldown, not a good damage output in early-mid game, so use it for mobility and escaping (You can target neutral monsters behind the wall, and you will survive).

Your W! Despair. This skill will make you and your opponents cry. AoE like an aura that damages over time. GREAT to take down tanks, since it hits a % of total health, and will be improved with your AP. Not a good skill to farm, but it can help...

Your E is Tantrum. With this skill, sad mummy will become a spinning mummy. This is your main farming spell. Its cooldown reduces 0.5 per hit that amumu takes. In higher levels you will love to go farm minions alone, without your minions there. And with Will of the Ancients, enemy minions will be your health pool. (and gold and exp.)

Your Ult!! Curse of the Sad Mummy is a very powerfull skill for a tanky champ. The enemy's biggest nightmare!
It makes all champs in range (huge range, btw) UNABLE TO DO ANYTHING for 2 secs, and dealing decent amount of damage. 2 secs where your team will crush opponents. Try to get as many champs as you can, and ALWAYS use your ult when you have a teammate near. Your ult will be useless if you are alone, unless you used it for stunning opponents (ex: they're ganking you in jungle) and then you ran away.

But try to only use Bandage Toss if you need to escape.

This build was created for people who wanted to 'Tank' (?) but deal good damage too.
This ISN'T full tank build, so don't comment ' Amumu is tank, this build is wrong -1', first read the title, or at least try it once.

And.... that is all for now! :) I'll try to improve it in time, comment please, i need opinions for feedback, and make this guide better :)

Soon, images!! (learing about that ^^ )

(This is my first guide, so i didn't search for images. I just wrote it in a .txt when i had no internet, and then i edited it a bit.)

I hope this build helps to the community :)