The Simi (Charonte for "baby") is Acheron's demon daughter. She first appears right after Acheron is brought back to life as a god. When one of Acheron's mother's Charonte demons gave her to him to care for, she was three thousand years old, the equivalent of three human years. She calls him her "Akri," which is Charonte for "master." She can also turn into a multi-colored dragon tattoo, and reside on Acheron's body. In her demon form she has red and white marble skin like her mother Xiamara.
Artemis calls Simi 'It' and Simi talks in the third person, referring to herself as "The Simi."