Therylassa is an elven cleric of Fharlanghn, and was the leader of the clerics and acolytes at the Shrine of Piety in Hammerdine.

In Codex III-Chapter 8 the party discovered that she was secretly a worshipper of Nerull. She attacked the party, and was killed in the ensuing fight. Afterwards, the Shrine was shut down by Hammerdinian officials.