I have no idea how an inkfish would create an illusion.
You seem to be trying to do something similar to Slyph (http://elementscommunity.org/forum/index.php/topic,21608), so that thread might be of useful reference. (Of balance theory, what has been suggested and what has not yet been suggested.)
when cuttlefish shoot ink. there are two types. One is just ink, it is similar to a smoke screen that makes it difficult to see. The second type is called a psuedomorph, it is a mucus bound ink that forms a shape similar to the shape of the inkfish. Predators get confused and attack the false shape instead of the cuttlefish. (this is usually accompanied by the cuttlefish changing color, which makes it even more confusing)
in general, this is different than the cloaking based skills, because you can still see and target cards. The point is to create confusion, because the enemy wont know which card would be really targetable, and which card would actually be a psuedomorph, represented by the card Psuedomorph on the field.
Edit: right now i have it that the inkfish can only upkeep 3 at 1 time. Im also considering making it so that the psuedomorphs only last for 3 turns.