When you enter the pet arena with your pet its like the same in the pvp arena just find a fight and when you in the fight its your pet against there pet the owner of the pets pick the cards
so i think cards should be dropped by other monsters and bosses and be bought as well these are not wizard cards there pet cards :)
so each player gets a deck of (as many cards as they have) then you pick a card such as Red Breath 120 D and the other pet gets hit
each pet in the whole universe of the game as a baby starts with 500 health whenever your pet levels up you get a +200 health
in the battles of pets there can also be ranking called PET RANKING if you lose you get 1 taco if you win you get 5 taco
Rank 1 (your begin rank) - Pet Struggler Rank 2 - Pet Robber (30 taco) Rank 3 - Pet General (70 taco) Rank 4- Pet Captain (135 taco) Rank 5- Pet Watcher (160 taco) Rank 6- Pet Overlord (280 taco) so you can also use tacos to buy other cards to use
also if you level up your pet for health +200 you can also rank up to make your pet get +100 health
there can also be cards with healing like this Grand Stealer +175
Well, I like it. :) But unfortunately for you and me the idea is too closely related to wizard PVP that KI probably won't make the effort to make it into a reality ...