They are after artifact stolen by SH.
oh right, duh. I guess I've been assuming that SH stole the arfifact from the mindflayer ship, but that actually doesn't make sense since she was trapped the whole time...
So wait, SH had the artifact. Had brought it back to BG3, almost completing her mission. But right before she delivered it, a mindflayer ship happened to spirit her away??? Talk about unlucky
Either way, this still supports my theory that Lae'zel is a complete nobody.