So I had a brief thought, how much of the Dark Eldar army could you make out of reasonable conversions from Age of Sigmar models.
Mandrake from the new fish elves have been discussed, Crypt horrors for grots is a classic, wych elves for wychs is pretty easy.
But then the daughters of khaine provide a few extra options with the new models, the medusa could be sslyth, the harpies could be made into scourges or maybe even hellions.
ghouls might work for wracks.
if put guns on the model, dark elves become kabalites pretty easy.
Talos and Chronos would take a bit more conversion, but they are kinda horrible stitch together monsters so some sort of kitbash of monsters could work great.
Vehicles seem like a problem, but I'm iirc the kharadon overlords skyships aren't that far off in size. And there is the skycutter.