Althea Duchannes is the daughter of Katherine Duchannes and James Harnett, sister of Emmaline Duchannes and the aunt of Sarafine and Delphine, thus being Lena and Ridley Duchannes' great-aunt. She was a Dark Evo, meaning she can morph into anyone she wanted and could also control whoever she wanted, like a Siren. She could also borrow the powers of any Caster she touched and Kelt.
When she turned sixteen and was Claimed by the Dark, her mother couldn't stand to send her away, and tried to keep her daughter with her, but eventually she was forced to after people in town got injured and a girl drowned. It became obvious that there was no turning back. Since then, Duchannes can't live with their parents until they're Claimed.
- Shape Shifting: As an Evo, she can look and sound like anyone she wants.
- Mind Control: As an Evo, she can control whoever she wants like a Siren. This power only works on mortals and less powerful Casters and doesn't work on more powerful or equally powerful Casters such as Sirens, Naturals and Cataclysts.
- Kelting: As an Evo, she can speak non-verbally with other Casters who possess the same ability.
- Power Borrowing: As an Evo, she can borrow the powers of any Caster she touches. Borrowed powers are unstable, the more powerful the Caster was they belonged to, the longer they last.