We can rule out the whole 'Wizardborn' idea because in Five Kingdoms Trillian (And Rammaro) both say that they come from a Non-Material realm (Not Lyrian) Of course, if we are going to say that they have to come from a world in the Brandon Mull universe we have a few options: Earth, Lyrian, The Outskirts, The Echolands, and The Other. We have already ruled out Lyrian, and for similar reasons, we can also rule out Earth and The Outskirts. This leaves us with The Echolands and The Other. While it is most likely that they don't come from a Brandon Mull world, we still have to check. We probably need to rule out The Echolands because there are not torrivors even though it is not physical and Cole can use his powers to do things similar to what Trillian says they can do. Also, Rammaro is stuck there so it is unlikely. Finally, we have The Other. We can not rule this out because we have virtually no info on it. However, She Who Stands At The Summit claims that an unnamed 'Great Evil' will come from The Other. This could possibly be a torrivor. This is the only evidence we have to support that they come from the Echolands. In conclusion, I think that they probably come from another dimension not listed here but The Other is always possible. Comment below to add your thoughts on the matter.