Mz. Ruby is a particularly cold and dark individual due to years of isolation in her early childhood. Despite her eventual use of magic in order to make friends, she later employed these abilities in a life of crime. She is somewhat maternal towards her zombie creations, calling them her children. Mz. Ruby possesses an eccentric and sadistic sense of humor, quite delighted at the thought of Sly dying. She had ambitious plans to use her dark creations to take over Mexico. Despite her great power and large build, Mz. Ruby is cowardly and opts to fight Sly from a distance rather than hand to hand. Additionally, when Sly used Chumley (at Mz. Ruby's insistence) to get close enough to strike, Mz. Ruby killed Chumley, either out of anger or bad aim. Later, one of the large mosquito guards helped Sly get to her in the battle, possibly suggesting that the local wildlife was angry with the priestess poisoning their jungle. Such instances further substantiate how a youth of isolation impaired her ability to care for others.

Mz. Ruby was born into a family of mystics and was feared by other children due to her strange powers. Despite an earnest effort to fit in, learning to summon the undead was the only possible method she had of gaining friends. Years of bitterness led an adult Mz. Ruby to use her voodoo talents to commit crimes, in order to take revenge on the world for fearing her as a child. She became the chief mystic of the Fiendish Five, which allowed the group to break both the laws of man and nature at the same time