Thetis is a villainess of the 2015 hidden object game Witches’ Legacy: Slumbering Darkness, alongside the series' main antagonist Morgana.
Story[]
In the game, Morgana tries to bring Thetis, a goddess-like (sharing her name with an actual Greek deity) "Mother of Witches", back to life through an evil ritual into the body of the protagonist Lynn. Outside of the introduction sequence, she only appears in a spirit form, almost possessing Lynn but the witches are defeated before she is fully revived.
Gallery[]
Artist's depiction
Referenced in Witches' Legacy: The Dark Throne