In DA1, the Green Man, Tamis Azkanikin, is "secret head of the outlawed Wizards' Cabal." He lives in Old North Watch, a crumbling ruin on the northern coast. He led a recent magic-users' revolt in Vestfold and continues to work with "the underground conspiracy known as the Wizards' Cabal" for the overthrow of King Uther and the return of imperial rule in the North.
In the 3e supplement The Wizards' Cabal
, the High Spellwise Ursula Zov led the Wizards' Cabal in siding with King Uther against Thonia, but some left the Wizards' Cabal and joined the imperial forces. We're told that in 1020, "an underground cadre of sorcerers staged a revolt in the city of Vestfold."
Taking these two sources together, it seems likely that Tamis Azkanikin was a member of the Wizards' Cabal who disagreed with Ursula Zov's decision to side with Uther, leaving the Cabal and inspiring a group of sorcerers to revolt in Vestfold. Escaping Vestfold, he allied with the Iron Duke, Taha Marcovic, and from his new lair in the ruins of Old North Watch he has built a secret organization bent on opposing Uther and his Regency Council. He might even call this underground organization the Wizards' Cabal, claiming that his group is the true Wizards' Cabal and Ursula Zov's organization is illegitimate since they betrayed the empire.
In this thread
I suggested that the Vestfold Revolt was staged by Tamis Azkanikin to provide cover for the abduction of Kvale Dram, who was then taken to be interrogated in order to learn the secrets of the Comeback Inn.