Okay, so that making Pokémon basically work like they also have class levels, and they could study class dominions what cleric class would be recommended for a ghost type that slowly devours your immortal soul. The longer you stare at its flame? Here are my best guess choices:

Death Domain,Grave Domain, & Light Domain That said, I am open to more suggestions!! Besides that this does apply to other ghostly clerics. It would be kind of interesting!

hmm, tough one. id say a variant of warlock perhaps, with the ability to reap souls for your patron for power.

Trying to go for a healing, sorry have not been on D&D for a while.