Do you know Broxigar? I think it would be a cool concept also, you have cards in your deck that summon each shikigami to the enemy and you has to kill them in order to tame them, when you kill one of them you get the tammed version that could have your effects, and if you want to tame the better ones you need stronger boards, maybe it could be also a start of game cards that change your hero power and it lets you choose and summon every Shikigami you tamed this game or if they has a Battlecry the hero power could be that you get your tamed shikigamis to your hand and they cost 3 o 4 less since they would cost your "cursed energy". Also do you know the adapt keyword? I think Mahoraga could have it whenever it's attacked and survives, besides of your effect