Author's Notes
Demons
I wanted demons which are chaotic. Every demon is unique, there are no "demon races", every single one is unlike all others.
They (probably) can't enter our world on their own, so they are constantly looking for summons, which basically invites them in.
I wanted them more physical, so I dropped the entire "sell your soul" thing. The want something more tangible, and whatever they want it is bad.
I added the "true name" thing, as a way to explain why summoners need to study rare and mysterious texts. Knowing the true name means that you know who'll answer. Summoning without a name is like setting up a blind date on the internet on a dark forest road in the middle of the night.