Sinnoch is one of the more unorthodox members of the Kastar Ghaash'kala, for Sinnoch is a Dolgaunt created by Dyrrn, the Corruptor. After Dyrrn's imprisonment, Sinnoch spent much time alone in Khyber, simply wandering aimlessly. Unlike many of their kin, they felt no inclincation to wage war on the goblinoids. Indeed, Sinnoch hadn't even realised the war had ended.
Sinnoch was later found by a Kastar patrol, who issued them the challenge despite their horrific appearance. Sinnoch, to their surprise (both groups), accepted and travelled back to Kastar Dar, where they joined the Ghaash'kala and took their oaths. Sinnoch serves many purposes within Kastar Dar, they have a gift for fleshcraft, making them the most unorthodox (but unsettlingly talented) physician in the clan. Additionally, Sinnoch was trained in martial arts during the Daelkyr War, and they now use that knowledge to help train the younger warriors of the Kastar Ghaash'kala.
Sinnoch is a legendary physician, flesh and bone are like putty in their hands. They can repair any wound, and fix any medical condition (eventually). They can even make more drastic changes to a patient's body, changing their appearance, regrowing lost limbs, or even changing their biological sex. As a result, the Kastar are exceptionally healthy, and they treat Sinnoch as they would family.