
I don't believe dark aether, in and of itself, comes from the void. The void is, if you will excuse the pun, void of Aether. That is why they want to come here so much, to consume the Aether of the material world (Eorzea of which is heavily saturated in it, aparently more than most), however, it could be from the void and it is simply a misnomer ascribed to it given that is the only thing to really compare it to from the material world.
As to where it comes from, Well, I believe the Aether in Pharos Sirius was corrupted due to the proximity and damage caused by the attack by Bahamut (the yellow crystals of aether piercing the entire tower). I think that the balls of Dark Aether are simply, either a more corrupted version of that. Or as I mention above, it could very well simply be a misnomer.
As to the Alchemy, I don't know that much, the mist does indeed look like Void corruption, either that or a manifestation of I.M.E Â or Individual Magic Effect (Read Goblins if you haven't
) which in essence is the individuals personal manifestation of Magic (a different coloured glow with funky stuffs)Â
And it sounds like a cool thought regarding the voidsent and trying to control them, better hope he keeps it quiet however, as there are people that would be knocking on his door to destroy him and his lab
As to where it comes from, Well, I believe the Aether in Pharos Sirius was corrupted due to the proximity and damage caused by the attack by Bahamut (the yellow crystals of aether piercing the entire tower). I think that the balls of Dark Aether are simply, either a more corrupted version of that. Or as I mention above, it could very well simply be a misnomer.
As to the Alchemy, I don't know that much, the mist does indeed look like Void corruption, either that or a manifestation of I.M.E Â or Individual Magic Effect (Read Goblins if you haven't

And it sounds like a cool thought regarding the voidsent and trying to control them, better hope he keeps it quiet however, as there are people that would be knocking on his door to destroy him and his lab

Aduu Avagnar, The Wanderer: Wiki