Since the two are different, is sounds like Gary intentionally conflated the two with his illustration on page 30 of Supplement I., which shows the statue, but is titled as "THE GREAT STONE FACE | Enigma of Greyhawk":
From what I gather, The Great Stone Enigma is the statue, and it's the free-standing thing, and it's NOT where Fraz was imprisoned. The Great Stone Face was set into the floor, and it is apparently where Fraz was stuck.
Correct--supposedly, nobody ever solved the Enigma, but a greedy character once used it (via a magic mouth) to bilk another! The Stone Face, on the other hand was straight outta A. Merritt--except it had a demon lord instead of an ancient god imprisoned in it! ^__^
The two terms refer to the same thing. The text on the bottom of the illo says, "The Great Stone Face Enigma of Greyhawk. The Frazz face was something completely different. Just some thing that EGG and Rob winged up on the spot while DMing for Ernie and Mark.
Hmm... you have something there, although the Enigma is in fact a whole head (based off an Easter Island carving--I often wondered whether the "enigma" was some kind of pun about Easter...), while Fraz's prison was indeed a large bas-relief carving of a face.... Hmmm. ^__^
Do ya mean the "Enigma" face or the "Fraz" face? AS to the Enigma, not really--only the funny story about the "Magic Mouth IncidenT". As to the other: Have you ever read The Face In The Abyss by Merritt, Amigo? Gary apparently lifted the idea wholesale from that book, but put Fraz in there as the antagonist. I believe that it was to eliminate some powerful magic items from his campaign--is that correct, Scotty? The mind starts goin' as we approach the 50 mark... ^__^
Oh, you need to read Face In The Abyss, but you should read Dwellers In The Mirage first so you can see where Gary got the idea for the EEG (although not til over half way through the book, I think!). Also, The Moon Pool--to get the reference to the pool to the "celestial deity" (Celestian ^__^) in CZ.