Identify "Urban Fantasy" Novel, Please

Reading another thread, someone mentioned Mark Helprin’s “Winter’s Tale”, which triggered a memory of another novel from around the same time period (early-mid 80s) that I can only remember elements of.

It was an urban fantasy novel, set on a college campus (and I can’t remember if it was an existing university or one created for the book). A creature of faerie somehow becomes attached to either a student or a professor and there’s some quest they have to fulfill, though damned if I can remember what the McGuffin actually is. The faerie took the shape of Mohammed, the Marschallin’s page in Der Rosenkavalier, with dark skin and turban, and was mute, like that character.

And that’s all I remember about it. But it’s bugging the hell out of me that I can’t remember anything else, especially the title or author!

Sounds like Esbae: A Winter’s Tale by Linda Haldeman
The spirit critter was named Esbae and its quest was something like to do a really great deed. It ended up saving the student girl’s life from a demon.

That would explain why the mention of Helprin’s “Winter’s Tale” triggered my memory! Thank you!