Quote Originally Posted by Enkidoh View Post
Thancred being incapable of using magic/manipulating aether had nothing to do with his possession by Lahabrea - it was Y'shtola's use of the forbidden Sharlayan spell Flow to escape the Crystal Braves and the Brass Blades in the Sil'dih Aqueducts which is what made him unable to cast magic from then on (basically Flow is an early crude form of teleportation without using an aetheryte to guide you through the Lifestream to your destination).

Flow is so dangerous it was considered utterly tabboo in Sharlayan (Matoya chewed Y'shtola out for her recklessness over it), and Thancred found that out the hard way when it aetherically altered both of them, altering his aetheric signature to the point his internal aether levels are so dangerously low he is now totally incapable of any form of aether manipulation in his body, even teleportation, which the game insinuates is a rather common spell used by a majority of the population (making him rather like a pure-blooded Garlean aetherically), as to attempt to do so would kill him.

You are correct though that it followed him to the First, and as a GNB he is completely reliant on Ryne making him his cartridges (one wonders then where he's getting them after his return to the Source), so maybe he should consider a career change back to ROG again or maybe GLA, as they wouldn't be so reliant on internal or external source of aether to power, but are purely martial.
Aaah yes you're right, I overlooked and forgot that fact !! Sorry :'(
But when returning to the Source I thought it was Y'shtola but indeed perhaps it's Urianger who fills his cartridges, though that doesn't change the fact he's still reliant on other Scions to fill his cartridges ^^