I'm pretty sure that the Dark Urge is a Bhaal Spawn. Especially after seeing what it seems very much like the Slayer form at 0:57 of the Release Teaser:
Slayer form was datamined YEARS ago.
I hope we get an Illithid-like Slayer form if we get regular slayer and tadpole together.
I see, but I don't think that this rule out the possibility of the Dark Urge being a Bhaal spawn. It matches the original games in the fact that you can succumb to the murderous urges that come with being the offspring of the God of murder.