Yvette was born to Aislinn and the demon, Baelrune. She was born with a twin sister named Nemesis. The two of them grew up in Toxin Raj, land of the Helkaer Commander. From an early age, her mother told her what her mission in life was and Yvette drank it in. She and her sister were always close even though they were polar opposites, personality-wise. Yvette was gleeful, bubbly, and full of emotion while Nemesis was cold, stoic, and emotionless. However, the two of them made a great team and trained and played together. When the time came, Yvette was told that Nemesis had to leave to go to Sly, the General of the Helkaer. Yvette was sad to see her sister go, but she knew that this was for the best. She said goodbye to her sister. She remained in Toxin Raj. When the war broke out between the Helkaer and the Neutral Kingdom, she wanted so badly to participate, but she was too young. With the Helkaer win, Yvette plans on going to Tremala Woods to infect the herd members with her Underworld disease. Before she heads off to Tremala Woods, she meets a foal in Toxin Raj. In another venture outside of Toxin Raj, she finds herself going to Eden, where she meets a stallion named Baby. The two of them become intimate and Baby comes to Toxin Raj with Yvette. A few weeks later, Yvette contacts her father, Baelrune. However, not long afterward, Baby disappears. Yvette is very disappointed at his departure and decides to focus her attention on the influx of two cambions in Toxin Raj named Utherin and Persephone.

In the next coming weeks, Yvette's plans start to unravel as Baby disappears as well as Utherin. She makes more attempts to get out and recruit, but none are successful. Frustrated at this lack of progress, she contacts her father, Baelrune, to ask for his advice. He gives her a much needed pep talk and Yvette is re-energized and determined in her plans. In one of her ventures out to the Free lands, she meets a fellow cambion named Sovereign. She tries to convince him to join the cause, but he declines, seeming to find her ambitious ridiculous. Yvette is not discouraged and continues on her quest. When Sly is attacked by Zephyr, Yvette is gleeful and eager to attack Lachlan Breck with the rest of the Helkaer brethren. She attacks the Royal herd, first attacking a mare named Davina, and then teaming up with Helkaer apprentice, Sage, to attack Keroscenic Hazard. She becomes closer to Sage, despite the mare not being a cambion like herself.

Tragedy strikes Toxin Raj when Yvette wakes up from her usual slumber in the cave to find it filled with smoke. Sage comes to grab Yvette from the cavern and the two of them flee from the fire currently raging through the Helkaer territory. Most of the herd ends up making it, though Respira is badly injured in the attack. Despite her home being in ashes, Yvette decides to stay in Toxin Raj and support Sage, becoming an assassin within her herd. She steps up her game, taking on discreet hits and spying throughout the Free lands. It is around this time that Yvette decides it's time to spawn her own cambion army. If she cannot find them, then she'll make her own. She approaches Xerxes, Lord of the Underworld, for a child. He agrees and Yvette eagerly awaits the results of their union, excited to start her army with Sage. Unfortunately, this arrangement does not last long when Sage disappears. Yvette is enraged at this development, going out to search for her leader and also keep the lands defended in her absence. When Sage does not return, Yvette is greeted by a very familiar face taking her position: her own twin sister, Nemesis.

She congratulates Nemesis on her new position and tells her sister of her potential pregnancy. Nemesis is thrilled (or as thrilled as she can be) and instructs Yvette to continue building her army and also to plot a raid on a Neutral herd, as well as the Versai land their half-sister used to occupy. In the next few weeks, Yvette confirms her pregnancy with glee. Yvette then begins to scout out the Free lands, running into a stallion and then into a mare on Mount Malvolia. She scouts out the Neutral land of Eacarrah to see if it's prime for attack.