Speaking of Silvertear, the end of the Monk questline describes it as "the aetherial center of the world." Erik, the MNK quest guy, even theorizes that magic BEGAN there. If magic and aether originally came from Silvertear, it is not too much of a stretch to think that it is the birthplace of the Primals as well, thousands of years ago.

Also, I know this is off topic, but it does have to do with Primals and this is as good a place as any to bring it up. Sastasha HM spoilers:

Upon completion of that dungeon, we learn that it is possible for a person to be tempered by a Primal twice. The second time turns them into abominations of aether, monstrous creatures that resemble the element of the Primal who tempered them. So, for Captain Madison and his crew, they were turned into tentacle-faced monsters like Davy Jones in PotC, since they were tempered twice by Leviathan.

I wonder what impact this could have on future plot developments.