ive never seen or heard anything that made me think they were brought form the portal worlds. they exist in all of the them.

now obviously lanfear was able to at least attract or control them somewhat within the portal world. not to mention finding out which one rand was in, assuming she didn't activate the stone in the first place

i think in that world, the trollocs won the trolloc wars but lost the grolm wars

and apparently there was some kinda of weave used that would fly around the world and burn out swathes of the ground whenever it decided to