I play a Great Old One Warlock - his patron is a living demiplane of knowledge that manifests as an endless dark library with something always lurking just out of sight.
He serves his patron by constantly collecting and sending it any scraps of magical, forbidden, or simply novel information he can find, so my DM hasn't really used the patron as a plot thread for anything yet, but I've been thinking about what my characters ultimate goal would be re: the patron, and I think he'd want to eventually be elevated to a favoured servant of the patron, something akin to a lich.
However, the lich doesn't feel Lovecraft-y enough, at least as it's commonly described. A Mind Flayer might be more appropriate (considering the GOOlock's telepathic features) but that still feels kind of wrong also.
Are there any other Far Realm/extradimensional/Lovecraftesque equivalents I'm not thinking of?