Lilly doesn’t have any fixed apprentice or for that matter gender. Though she has a tendency to take the form of attractive women, she has at time taken male form. In her d’monic form she looks very much like what a stereotypical succubus looks like. Large bat like wings, clawed hands and horns.
Thousands of years ago a demonic academy pooled their knowledge, skill and time to summon Lilly into existence. Tomes and grimoires both ancient and modern where consulted, scholars and expert demoligists argued over every nuance of the ritual that would bring her into being. The considerable investment into her creation was done with a single intent so that she would venture out into the world and gather new knowledge for the academy.
After her education she boarded a D’monic star ship (itself a d’mon created for such a purpose) and traveled to prehistoric earth to research humanity. The study was meant to be a simple one, use her shape shifting abilities to blend into human society and make a long term study of humanity as it evolved culturally and genetically.
Well that was the plan but in the middle of her project the Scourge invaded. While Lilly’s immortal nature means she has little to fear from death the Scourge’s ability to capture a person’s will holds particular terror. If infected by a scourge parasite she would never be able to complete her research and present it to the academy.
After her escape from earth on one of the Theseus’s shuttle craft. She has continued her research with the humans that are part of the human diaspora but her deepest desire is to return to earth (hopefully now free of Scourge) so she can complete her research.