: According to GURPS Myth, humans claim the Bre'unor are
: renegade Fir'bolg and the Fir'bolg claim they're
: renegade humans, though it's speculated that they may
: be a third distinct race sharing the general features
: of both.
: The masks do /not/ come off, and most scholars believe
: it's magically fused to the cultist's skin in a dark
: initiation rite.
In other words: No.
But that seems to be as close to "canon", on the level of canonity that GURPS Myth has at least.
Of course, just to be really weird...
Bre'unor are a seperate race (most of which we don't see or know)...-and- the masked ones are cultists.