From what i've seen with the most recent of released Champions we have:
= Mage.
= Marksmen.
= Fighter.
= Support.
= Assassin.
All we're missing now is a new Tank Class Champion, if this Tamm is a legit Champion_ (which i really am hoping it is & not a internet troll)_ then it's most likely so that he is gonna be the newest Tank. as for his role Tanks are usually given either the Top Lane or Jungle position (rarely getting Bot lane as a "supportive" champion...& going by his personality in the video i doubt Tamm is the supportive type).
Now going by Tamm's appearance alone (from what we can see in the drawings on the pages in the video) & from what we see of his personality in the Video me personally he might be a Roaming Melee AD Tank Jungler that could be a Top Laner that has incredible survivability by means eating everything in his path to maintain his Health & give him self-Buffs rather than just being bulky.
I'm just gonna rattle off what his Abilities could be:
Q-Ability: Lurk/Gulp.
[think Rek'Sai Burrow Ability but he remains "underground" for a limited amount of time but he is Invisible, at the end of the Lurk's duration or on his next Auto-Attack Tamm erupts from the ground dealing Physical Damage to all enemies in a small radius while also Healing himself by a small amount per enemy Hit. if he kills an enemy with the Gulp the Heal is doubled & he gains a small Buff for a short time]
Thoughts Why this Might Work: having a tank that can go Invisible & be able to sneak up on target & then erupt out of nowhere & then start disrupting the enemy team could be a powerful Initiate or a way to clean up large team fights.
W-Ability: Slurp Down.
(in the Video if you look closely Tamm has a long tongue that he seems to use to pull victims in)
[this could either be a Skill-Shot or a Point-Click that has Tamm pull a target into his mouth where the Target is Stunned for a brief moment after being dealt Physical Damage, for the duration of the Stun the target remains in Tamm's mouth & he can move around while he has that Stunned target but that enemy will be Untargetable for the duration. at the end of the Stun Tamm spits out the target dealing either additional Physical Damage or dealing Magic Damage]
Thoughts Why this Might Work: Tamm could use this to take out an important player on the enemy team or snatch up a fleeing enemy & take the target to Tamm's team to gang up on the target or allow Tamm to wail on the target after spiting the target up. disruption & crowed control.
i'm gonna stop right here with the Abilities, but if you think i'm on to something or have a comment about these Abilities then please Reply.