Mynce, like Rayne, is a dhampir, the offspring of a vampire and a human. She taught the younger Rayne how to use her innate abilities, and served as her partner and mentor on Brimstone Society missions. In the game's introductory chapter, set in Louisiana in 1933, after slaying many mutated humans and strange demonic creatures, Mynce is caught unawares from behind and swallowed whole by a creature called a Maraisreq, which escapes before Rayne can murder it. She swears vengeance, and goes on to murder the Maraisreq queen, exterminating the race and avenging her friend.
However, in the game's third act, set years later in a castle in Germany, Rayne discovers that the mysterious second-in-command of the Gegengeist Gruppe, the Nazi organization she has been sent to destroy, is in fact an alive-and-well Mynce, who somehow survived the Maraisreq's stomach. When Rayne confronts her, instead of offering an explanation of how she survived and why she is suddenly a Nazi, Mynce attacks her, only to be thrown off a cliff by Rayne.
As it turns out, the dhampir had escaped death again; she appears to Rayne later on and reveals that she was in fact a double agent, placed within the G.G.G. by the Brimstone Society to gather information on their activities. To prove her story, Mynce reveals that she has killed several of the officer's on Rayne's hit list, and gives her their bloody dog tags as a souvenir. Joining forces again, the dhampirs search the castle for Jürgen Wulf, the evil leader of the G.G.G.. Unfortunately, they walk into a trap, and are separated by a porticullis, at which point Wulf uses his superhuman strength and speed to suprise-attack Mynce, easily overpowering her and tearing out her heart, making it pretty clear that she was really dead this time. Once more, Rayne swears revenge, and once more, she gets it, murdering Wulf in the climactic boss fight.
Being dead (for reals), Mynce made no appearances in BloodRayne 2, and no reference was made to her.