Instead of having a pet or familiar, why not do something like this idea by Evil Hamster (that I stole and tweeked)?
http://elementstheforum.smfforfree3.com/index.php/topic,392.0.html (
http://elementstheforum.smfforfree3.com/index.php/topic,392.0.html)
Instead of choosing:
Mark + deck of cards..
we would choose:
Mark + "Special Ability" + deck of cards.
This "Special Ability" wouldn't be tied down to our Mark, and would be able to choose any of those abilities Evil Hmaster listed in his original post.
"Special Ability" could be indicated by some kind of icon (Sword, Skull, Sun, etc.) that would be on top of your mark.
I really REALLY hope this game doesn't introduce any cards or fluffy bunnies that will level up. That would be a REALLY BAD idea. Anything that encourages grinding is bad. If people want to grind, they should go find some Korean MMO. CCG's should be about many different cards and deck building, not about who has grinded the most. It would really suck if your opponent wins just because he has been playing for 5000+ hours and has a level 100 Fluffy Bunny of Death (see picture 1).
Picture 1.
Level 100 Fluffy Bunny of Death.