SOLVED. SF/Fantasy MC goes into cave and creature falls on his head, enters brain, becomes his friend...1980-1990?

[Blondish And]

Main Character is visiting a planet and sees some bad guys (hostile natives or something). He runs into a cave to hide and only when a creature falls from the ceiling onto his head does he remember that most caves on this planet are infested with these things that fall on your head and kill you. The legend is something like, For Every 1000 Men Who Enter The Caves, 999 Will Die.

Then he wakes up and finds out he somehow survived--only to hear a voice inside his head and realize that the creature is now sharing his brain.

He eventually comes to terms with it, and names it something like Pard, or Pal. And Pard or whatever can (with permission) take over his body and study a language or something while he sleeps, and he is able to access this information. And Pard can repair injuries to his body.

I think the author of the book was really prolific, like Piers Anthony or Orson Scott Card or something. I read it in the late 1980s I think, but it could have been published any time before that.

[Blondish And]

Well. This is embarrassing. I normally remember all the books I read, and it is really rare that I can't, but this one's been driving me nuts all day. But about 90 seconds after I posted this query, I remembered! It is Healer, by F. Paul Wilson. Sheesh. I'm an idiot!

Anyway, it was a great read, and clearly can be read as a standalone since I had no idea it was part of a series!