I don't show enough of these sketches I make in an actual book...
Fleur has a variety of servants/creatures that she can conjure to fight, protect, or even perform tasks for her. They are sentient, intelligent, and only obey her will. Most of them are simply conjured using her raw Ebonn magic (that black goo) and she shapes them to her tastes. Other times, she requires a vessel.
Her more powerful, specialized servants are such creatures that require her to "infest" with her power, take control of their minds by driving them mad, and then finally, when their will is diminished, she transforms their bodies into horrendous creatures with no minds of their own. Since these specific servants still contain a soul, they possess much more power within them, and are usually very large in size. For that reason, to summon these, Fleur needs to swap to a different Class (her Summoner form) that focuses on magical conjuration at a reduced cost of energy over any other stat. The downside is that despite the reduced cost of power required to summon these powerful minions, summoning them still decreases her sanity, leaving the True Goddess an opening to take over.