This C'Thun is a Token. You are looking for C'Thun.

We aren't 100% positive of the intention of this token card, but it is listed as a "Proxy C'Thun" which leads us to believe it is used to track your C'Thun's stacks from the various C'Thun-buffing minions.

Card Text

Battlecry: Deal damage
equal to this minion's
Attack randomly split among all enemies.