I agree with TII. I would personally keep pets more off-combat oriented, but it's a personal idea. If you make them combat oriented, though, limit them to AI matches. Possibly add a PVP3 option for pet duels, but... yeah.
I think off-combat pets could be cool. You could have a pet that grows with your battles, gains experience, and has some side effects that enhance your gameplay. For instance, you could have your pet:
- increase score you gain
- increase electrum you gain
- make you gain Relics somehow
- let you gain rares on a difficult task or lucky chance
- allow you to play different AIs or possibly give quests
Some ideas for combat-oriented pets:
pet reduces the cost of retreating - you lose less money in a lost duel
pet gains extra experience for every death effect you trigger (probably broken, needs a cap)
pet makes the AI have a chance to misplay its cards
pet reduces your and your opponent's HPs.
pet increases your hps.
pet allows you to see your opponent's hand.
Another possibility is to have pets - or elementals themselves - have different means of transport based on the element - a WoE ripoff - that allow you to reach "hidden areas" of the game, probably with specific quests. You need to gather all 12
pokemons pets and train them to reach all the areas (
and catch them all).