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Athrys is a Fallen who was once the lover of Eramis, Kell of Darkness. The pair admired each other deeply, with Athrys finding her partner's strength and stubbornness endearing, and Eramis cherishing her gentle nature. They lived together on the Eliksni homeworld of Riis before the Whirlwind and had many hatchlings together. Athrys was fond of the blooming water flowers native there.
She was apparently an artisan and builder of some renown, though what exactly she created is unknown. Variks, the Loyal described her as kind, wise, and clever, and the two had a substantial friendship before their exodus. 
Given Athrys’ absence at Eramis' side later on, and the latter's nightmares regarding her, it is implied that she disappeared or died during the Whirlwind.