This character shows up in the Looming Gaia story "Troubled Tides". It can be read for free here: https://archiveofourown.org/works/2.....pters/52197979

In that story, Sleater is referred to as an "it" because the protagonist can't determine her sex and doesn't really consider harpies "people" anyway. This is a common attitude around the Looming Gaia universe. Harpies are monsters created by the divine of thievery, Varas. Like many monsters, they are very imperfect creatures.

Harpies are known for being vicious and unintelligent, but Sleater and her sister Kinney are so horribly feral that even other harpies want nothing to do with them. They were forced out of their clan and found refuge in a secluded island off the coast of Noalen. That's when they run into Alaine in Troubled Tides. Alaine breaks Sleater's beak and leaves her for dead...but there is no confirmation that she nor Kinney actually died. We may just see them again in a future story. ;)