Just like Zaria, Milla is also a witch and wants revenge for being sent to the underworld for so many years. She comes from the same dimension as Zaria and she seriously wants to get rid of the Senshi twins as well as the rest of them. Occasional time she will go off on her own and attack them when she’s not supposed to. But that changes once her, Zaria, and Aline finally stole the power of the Silver Imperial Crystal and Sailor Star Imperial Crystal powers to try and destroy Domino City, Japan and the rest of the world. And of course they didn’t succeed in ruling. The Sailor Senshi stopped them.