: Well, in Myth 2, yeah, of course. They were brought forth
: from the Tain by the Summoner. That doesn't mean they
: came from there, because it was Connacht that
: originally trapped them there.
: dm!
So the question of their origin remains. In a world populated by trow, dwarves, and ghols, I don't see why the myrkridia couldn't have evolved naturally. Fetch are from another dimension, but do they even have physical bodies? You never see a fetch not wearing such skins, so entities that unusual could come from outside, but myrkridia have visible, physical bodies. They don't need to be explained as extra-dimensional beings.
"...and their right hands were raised in menace against mankind." sieg zeon