I think it's
possible the elves did come up with it originally, in a way that doesn't require the update's mentioned soap-bubble-like merging that puts the Apparition's soul next to ours and both being coated in the Wind. Or that maybe an Elf had a mishap and only became able to cast Chamon, and they decided they'd get wacky with it - wizards and hubris go hand in hand.
But... The repeated emphasis on the theory that Apparitions may be fear spirits, specifically the fears of wizards wearing a groove of sorts in the Aethyr, now makes me think that if
that's actually the case, then Gehenna's Hounds are
probably a human thing. Elf wizards wouldn't have the same kinds of fears human wizards would.
To take some examples:
- The Handmaidens are feared to be the souls of burned witches - straightforward enough. Them appearing from doors or windows or other portals is probably tied to that - a paranoid wizard who might be afraid they would get burnt at the stake might also fear that the next person who knocks the door or appears at a window might be an enemy.
- The Dark Hounds probably represent the fear of either being hunted down like an animal by people who fear or hate you for having the destructive potential that magic offers, or being treated yourself like a dangerous dog due to said destructive potential. More prosaically, this is probably associated with the a fear of a literal giant animal hunting you down.
- The Rider in Red, as was said in the first part of this Apparition-binding action, is speculated to be representative of wizards having their existence bound solely to war, and also perhaps the fear of being a priority target for cavalry.
- The All-Knowing Serpent/Wisdom Asp, Boney has said, is probably representative of the fear of "Becoming so changed or entranced by a Wind that you stop seeing its dangers or forget who you originally were", and is also probably a fear that you'll get ambushed if you lower your guard around everyday objects.
- The Lost Child appears as the sorrowful spirit of an executed youth with a charred garb - I would personally presume that's the fear of being abandoned by one's guardians and killed at an early age simply for having magic, not even doing anything with it.
With perhaps the exception of the Rider in Red, these are mostly human-centric fears. Elves don't fear being burnt by their fellow elves simply for having magic. Elves don't fear they'll be hunted down or become weapons of war merely for being good at destructive magic. They generally keep a centered point of view and in general wouldn't be afraid of being too bound to a single Wind. And, certainly, they would not fear being abandoned and killed by their fellows simply for having magic.
I suspect that if this is the case, then Ulthuan probably doesn't have Apparitions, or at least none that we know of canonically - that if they'd have some, they would have to be quest-original. And as such, that greatly lowers the possibility of Elves having made it. At best, you could speculate that an elf living among humans saw the Dark Hounds and was like 'you know, I can probably take advantage of this'. But I'm not even sure an elf would lower themselves to
that.
So IMO it's probably a human who did it.