Just writting this down while it's still in my head:
So Dvesel's ancestor wasn't always called The Plague Monger. She was actually a very kind and caring jadeblood that did her civic duty by rearing the mother grub and tending to the needs of the hatchlings in the brooding caverns. It was when her predecessor suddenly died one evening that she was haphazardly thrust into a position she wasn't ready for. She was then approached by a high ranking official (Zeraki's Ancestor/The Constructor at the time), claiming to be a scientist sent by the Condescension herself to collect specimens for an undisclosed purpose. And that her predecessor had been privy to this knowledge before their death. Bound bound by honor and fear of death, she'd forgo her duties and provided him with newly hatched grubs.
But not just any grublings: Mutants. Any grub that showed signs of either malformations or obscured blood color were whisked away under the pretense of being culled.
In the time of her predecessor these mutants were being used simply as test subjects. They lived just a few sweeps before being disposed of. But when Dvesel's ancestor took over the grubs were instead being cared for by the same doctor that first experimented on them. Hundreds if not thousands of grubs would be rescued from the culling fork. Their lives made simple by a Blueblood in love with a Red.
And everything was good for several sweeps until the doctor lost his mate to an early demise. Around that time Dvesel's ancestor began a torrid love affair with the doctor.
So completely distraught with the death of his matesprit he took out his fury on the jade. Turning her into a test subject sheerly out of spite. Breaking her mind and turning her into a hateful, horrid creature that was forced to hide her face behind a mask. In her escape she vowed to seek revenge on the troll who broke her and all his kin.
Taking up alchemy along with dark arts she created dark, terrible plagues and unleashed them upon cities and villages. Moving from troll occupied planets to the next, spreading diseases and blights. Scarring the land, ruining the soil and bringing fledgling colonies to their knees.
She became a cannibal, feeding on death and the weak. Living for many sweeps, just managing to elude her would be killers. Managing to just one day vanish without a trace.