Though a definite "baddie", Phirra is not the worst of the worst. She's in it for revenge, which she figures is a little better than world domination, though it's not exactly a noble goal. She maintains a sense of humour in even the darkest of times, and particularly enjoys making jokes of things which could quite easily kill her. She's confident in her abilities, to the point of minor arrogance, and the best way to convince her to do something is to tell her she's not capable enough.

Phirra grew up in Ajeshna, a land far enough from Camelot that it was quite safe and even prosperous at the time. Her father, Daxus, was one of the greatest magical researchers alive, and it was only a year after Phirra was born that he made the greatest discovery of his life: he found ways to reliably harvest, store and use the substance Ether, which had always been in abundance in the atmosphere, but completely useless until now.
His discovery didn't change the world at first, but it spread quietly, moving from a niche market that the eccentric rich would enjoy to something produced on an almost industrial scale that even the barely well-off wouldn't be caught without.
Phirra's childhood was spent in relative wealth. Her family was hardly nobility, but her father's discovery had made them quite rich. She had a tutor, but it was Daxus who taught her about magic and Ether, as there'd hardly be someone better suited to do it anyway. Phirra took after her father in that respect, and by her teen years,
she was also his apprentice and an amateur artificer.
When she was 15, however, a violent revolution took place in Ajeshna. The council that ruled it were on the back foot, but employed Daxus and a number of other artificers to produce a new device to fight the revolutionaries. It was they who invented the automaton. Soon, the council's army was replenished and continued to grow faster than any human army ever could.
The revolutionaries, in response, were forced to sabotage the factories that had begun appearing throughout Ajeshna. To stop them from being repaired, however, they also need to kill the council's artificers, or they would get nowhere. On the top of that list was Daxus. The house they lived in was burnt to the ground, and only Phirra made it out.
The plan succeeded, and the revolutionaries won. Ajeshna became a highly militaristic, imperialist nation ruled by the leader of the revolution, a man named Armas Quent. Phirra wasn't content to let this be, though. Armas had ordered her father's death, and she planned to pay him back in kind. She went through dangerous self-operations, creating experimental Ether devices that were a part of her from stolen parts. Now let them try to confiscate it all, she said.
When she was finally done, she made an attempt to break into Armas' palace and kill him. She didn't know enough about what she was doing, thinking her gear would make that up. She was wrong, and was captured as a result, though she escaped before the end of the month. Learning from her mistake, she fled the land, taking on easier contracts as a professional assassin, learning the skills she needed for it. Someday, she'll return to Ajeshna and take revenge for her family, but for now, serving Lancelot serves her interests best.