[@KatherinWinter]
anything except the celestials that requires the keys. limited by his concentrating, the contribution, and his personal knowledge, the more he learns about specific things he could wish to call forth, the more he can do. so example if he knows nothing about a chimera yet wants to summon one, he can't. he has to look into research to learn what he can about a chimera before he can figure out what he needs to do to form the contract, then having/doing what is required to summon it forth.