I always enjoyed this aspect of D&D games: the creative, interesting enemies, places, and artifacts that you could find in some of the books/tomes.

In fact, i was able to find the exact book i was thinking of at archive.org! The AD&D 2nd edition Book of Artifacts: https://archive.org/details/tsr02138add2ebookofartifacts/mode/1up

Here's one of my favorites from the book, though it's been so long i really could do to give in another gander: