From everything I've seen, it seems to be the consensus that grolm came from the Portal Stone worlds, and that the Seanchan found a way to bring them back to the real world; by extension, it could be reasonably thought that the same is true for s'redit, torm, raken, etc.

I've never really seen any evidence for this, though. Yes, grolm are in the Portal Stone world with Rand and co. Or are they? From what I saw in my recent re-read, they seem to be fabrications wrought by Lanfear to push Rand toward using the Power and seeking glory. When he kills the few they initially see, there are suddenly hundreds more that conveniently herd them toward the return Portal Stone; the only way out would be to use the OP to either kill them or escape.

Now, she certainly knows about the Seanchan, and is mentioned in connection with them in the Dark Prophecy. My thought is that she simply used illusions/Mirror of Mists to make the three or four Rand fought (or are there possibly similarities between the Mirror Worlds and T'A'R? Hmmm...). The actual grolm and corlm and torm and whatnot are just indigenous animals from the other side of the Aryth Ocean.

What do you all think?