Mission 7: Final objective doesn't complete after beating the priestesses

I have defeated all the waves of dwarves, Rhaskos' core is at 5000/25000 and has taken zero damage, and every single dwarf is wiped off the map.

I captured and converted the boss dwarf, and captured and converted three out of four priestesses.

I've beat the level once before so I know the event is supposed to trigger and spawn the hand of kira, but it never does. Not sure what happened differently this time, the level is easy enough to complete.