Based on my recent story chapter, Mukuro gets turned into a Grimm, similar to how Salem had made The Hound, only...Mukuro doesn't keep her name. As a result Salem gives her a whole new name. Lupus Caelestis, which is Latin for Heavenly Wolf.

Mukuro’s age is unknown, but pre-Grimm transformation she was 20+

Currently, I am doing a filler Arc for my story.