Holy Shit i'm gonna main Tahm mid
Just look at his Ap Ratios
6 sec Cooldown 50/55/60/65/70 Mana Damage the first enemy hit for 80/120/160/200/240 (+0.8) magic damage and slow them by X% for 2s. Champions with 3 stacks of An Acquired Taste will additionally be stunned for Xs Activate Devour while your tongue is in mid-air to devour monsters/minions from a distance.
Devour (W)
90 Mana
20/18/16/14/12 sec Cooldown
Devour a target for 4/4.5/5/5.5/6s (half that for enemy champions.) Enemies are dealt X% (+0.8%) of their maximum health as magic damage.
Enemy Champions:Requires 3 stacks of An Acquired Tasteto be devoured. Tahm Kench is slowed by 95% while holding an enemy champion.
Allied Champions:Tahm Kench gainsX% Movement Speed toward enemy champions while holding an allied champion.
Minions and monsters:Reactivate to spit, dealing 100/150/200/250/300 (+0.6)magic damage to targets hit.
X's are numbers that S@20 haven't found yet, I'll update when they will
Regardless, this champion scales very well with Magic pen because all of his abilities deal some sort of magic damage along with Nashor's Tooth
which would leave him with a healthy mana pool, +400 raw AP, more Mpen than you could possibly need, and roughly 1200-1600 extra HP (depending on how Abyssal's rework turns out).