Complex sentence: Henoch has completed an artificial body for Thalassa, but she refuses to transfer her consciousness into it, and instead offers to save Kirk, but only if she can keep Mulhall's body.
Split into simpler sentences: Henoch has completed an artificial body for Thalassa, but she refuses to transfer her consciousness into it. She instead, offers to save Kirk, but only if she can keep Mulhall's body.