Shiv

Harm none, and do what ye will. 

Not even if they have harmed you first. Not even if they destroyed the other half of your soul and left you empty inside. "Harm none," Mother said, "lest you risk bringing that darkness back upon yourself threefold."

Everyday Siohban asks herself what harm the darkness could possibly do. She's already dead inside. She died with her sister, and she'll be damned if she's going to let Maeve's killer get off scot-free. Even if it means an eternity of torture, her soul damned to suffer, she will avenge her sister and make Alejandro Tapia rue the day he was born.