Alchemy can certainly have nefarious uses and I think lore supports this pretty well throughout the game. So your second point sounds perfectly viable via lore and sounds like a very interesting plot point.
As for your first point, I have to agree with Nako'li in that the Void is devoid of Aether, hence why Voidsent are desperately trying to claw their way into our world. As for the origins of "Dark Aether" I haven't the foggiest. We see a good bit of corrupted aether, which is really just dead aether that has lingered too long in one place and cannot return to the Lifestream. This usually is caused by massive aether shifts which cannot cross the Aetherial Threshold and is trapped in our world. This causes such apparitions as ghosts or revenants or corrupted aether crystals. In some cases, lore notes these corrupted aether shifts can drive wildlife mad or mutate wildlife in abhorrent ways.
But as far as Dark Aether is concerned, I struggle to think of a place where it's mentioned besides T13, so as Nako'li said, it could just be a misnomer or it could just be something available to Elder Primals. There's so much we don't know about Elder Primals that it's hard to say. As such, I would recommend being cautious when delving into something we've only seen evidenced by an Elder Primal. It's an interesting plot point though, to be sure.
Last point, as for the aura that appears the Ebon Claw, a similar aura also appears around Ascians or thralls of Ascians in both 1.0 and 2.0. Is this a hint that the Ebon Claw sold his soul to the Ascians or that the Mad Alchemists' plot was actually a plot for the Ascians? We may never know, but it sounds like something the Ascians would do.
As for your first point, I have to agree with Nako'li in that the Void is devoid of Aether, hence why Voidsent are desperately trying to claw their way into our world. As for the origins of "Dark Aether" I haven't the foggiest. We see a good bit of corrupted aether, which is really just dead aether that has lingered too long in one place and cannot return to the Lifestream. This usually is caused by massive aether shifts which cannot cross the Aetherial Threshold and is trapped in our world. This causes such apparitions as ghosts or revenants or corrupted aether crystals. In some cases, lore notes these corrupted aether shifts can drive wildlife mad or mutate wildlife in abhorrent ways.
But as far as Dark Aether is concerned, I struggle to think of a place where it's mentioned besides T13, so as Nako'li said, it could just be a misnomer or it could just be something available to Elder Primals. There's so much we don't know about Elder Primals that it's hard to say. As such, I would recommend being cautious when delving into something we've only seen evidenced by an Elder Primal. It's an interesting plot point though, to be sure.
Last point, as for the aura that appears the Ebon Claw, a similar aura also appears around Ascians or thralls of Ascians in both 1.0 and 2.0. Is this a hint that the Ebon Claw sold his soul to the Ascians or that the Mad Alchemists' plot was actually a plot for the Ascians? We may never know, but it sounds like something the Ascians would do.