
There's a reason I see him as a parasite to her.
Mitron then forcefully merges with Gaia to become Ascian Prime
Gaia within the Ascian Prime manages to make a message, the red ball, to communicate with WoL and Ryne.

Ascian Prime then proceeds to start showing several of Gaia's memories as crystals and crushing them. This is another big reason I see him as parasitic to her. He wants to delete her to have his dead lover back. It's sad and unfortunate what happened to them but that doesn't give him the right to hurt someone else for it.
Emet hadn't been reborn yet. His soul was still fading thus he calls himself and Hyth "half faded souls of the dead." Once his soul is reborn that new person won't remember Emet's life. In fact the guy from Sharlayan explains that magics blocking memories fade before the memories do. So it's really no surprise that Emet knows what's going on in that UT scene.