It's a catfish with a top-hat my life is complete. The reveal page:

Tahm is described as a solo laner or a support. He uses mana, and given that he attacks with his tounge, he is probably melee ranged.

The abilities:

Passive-An aquired taste:

Allows interaction with the Q and W at 3 stacks. By putting extra power into a 3-stack passive, they create opportunities of extra power as well as extra counterplay. It also allows them to put more power in the rest of his kit, which is (depending on the numbers) pretty crazy.

Q-Tounge lashe:

Deals damage in a line to the first unit hit and slows it. If a champion has 3 passive stacks, it gets stunned instead. A fairly standard ability, allowing you to poke in lane and set up for ganks. Nothing too special, but you attack with your tounge so you get extra style points.

W-Devour: Literaly devours something; 3 options

A-minion/monster--> you get to throw is away dealing damage. 

B-allied champion--> protect an allied champion from damage and CC, and you get to walk around with him.

C-Enemy champion--> IF your opponent has 3 stacks of your passive, you can swallow them, allowing you to walk around with them for a while, after which you release him and deal a big chunk of damage.

This will probably be this guys bread and butter. The minion for more poke, probably the version you will use the most. Eating an allied champion is amazing as a support, your opponent lands a nami bubble? OMNOMNOM Well that ability is useless now and we will counter engage now that your most important engage is gone. A bruiser is trying to dive you? OMNOMNOM Now let me reposition you to a safe place. It sounds great, but it requires communication. And I really really like that. Riot brings out supports (Tahm and Bard are who I'm pointing at now) that change the way you play the botlane (in a different way from just which champions you play). Finally the Enemy champion version, In the little teaser thingy, you see him eat a twitch, then spit him out dealing a ton of damage. Personally, I think that it's pretty much impossible to attack a "high priority' target 3 times for you to W them. I expect this part to be mostly used to eat the (melee) support in lane so you can engage on the adc, or to eat a bruiser that tries to dive your adc in a tf or skirmish. It can deal a lot of damage, especially because it's %health, but it is going to be very hard to get off.

E-Thick skin--> Damage you take is converted to "grey health". Passively, after a while being out of combat, a part of your "grey health" is regenerated. As an Active, you can convert all of your grey health into a shield for a short duration.

In my opinion, at least on paper, this ability is absolutely INSANE. Poking will be less efficient because you regen a part of it, all-in's will be less effective because lost health can be lost twice! And the best part about it is that there is still counterplay in it! Especially in teamfights, you try to force Tahm into using his E, the shield activates, you ignore him for ~2 seconds, the shield pops and all that grey health is gone, and you go back to killing him. "dont focus the support/tank" etc. aside, I thing that both the potential amount of power, as well as the potential counter to it, make for a great ability. (It's still a bit insane though)

R-Abyssal Voyage (oh mah god it sounds so awsome)--> Passively, all your damage scales with your maximum health. Actively, it's basicly a two-man teleport. You open you mouth, an ally can jump in (or you travel solo), and then you teleport to a place on the map. 

This creates so much potential. You can eat the jungler and go for a gank, you can eat your adc and evade a 4-man gank. And because of the passive, you get rewarded for building health. Awsome ability, if it is OP or not is dependant on the numbers. 

All in all, I am really excited for this champion. I like tanks, I like supports, I like tanky supports, thus this champion exites me massively. He has great potential to do big things, I doubt he will be massively oppressive, that depends on the numbers. But there is defenitely counterplay possible, and I like that. I think we'll see him more as a support then as a top-laner, since I don't think you can use your W on enemy champions a lot if they learn how to play against you, and he sounds like such a good peeler for your adc.

It seems like TotalBiscuit finally got his champ with a top hat, and it's a freaking amazing one!

What do you thing about Tahm? What will his main role be? Will he see compatative play?