In September, 2018, I received an email from Mooky Makooky asking me about a Blood Omen detail I'd never actually noticed: the Flay Spirit Forge cave entrance has a statue on top. Mooky Makooky asked if it might be Pazuzu, an ancient Mesopotamian demon.
The prerelease build of the game from 12 July, 1996 has the same statue over a second cave, the entrance to Deleted Dungeon (M51, S00 and S00).
I believe that these statues may have originally indicated which caves contained Spirit Forges. In known versions of the game, those are the only caves consistently associated with demonic figures. However, there is very little evidence one way or another at this time.