Pretty sure you don't even need to complete the trials smirk

The answer you're looking for is in the books.

Put the books you think is the answer of the riddle in the socket.

The books are all over the library.

Councellor Florrick's favorite Warlock.

Back Black Geyser's DLC: https://www.kickstarter.com/projects/grapeocean/black-geyser-dlc-tales-of-the-moon-cult (RTwP Isometric cRPG inspired by BG1).