A member of the Jhereg Council. Terion was "wiped out" (but apparently not permanently killed) by Mellar during his meteoric rise in the Jhereg Organization.
Terion also supported Vlad Taltos after Vlad killed Tagichatn and started operating his own territory in Adrilankha.
Later, Terion was one of the contenders to replace Curithne as head of the Council. His mistress Triesco, a member of the Left Hand of the Jhereg, attempted to support him in this ambition.
Vlad's plan to get the Left Hand off his own back required the help of The Demon and therefore defeating Terion and Triesco. This left Terion as Vlad's enemy. Terion reminded Vlad of his enmity by trying to shine Kragar while Vlad was his guest.
Ironically, Terion's interference in Vlad's affairs proved to be his undoing. His presence and active enmity stood to compromise Vlad's plan to settle his differences with the Jhereg council, and killing a major Jhereg Organization figure turned out to be a useful part of Vlad's plan too. Terion found himself in the unfortunate position of falling under Vlad's blade after being set up by Vlad and his chief lieutenant, Chesha.