The Stockwood Scrolls
A legendary figure, the powerful lich Szass Tam is the Lord Regent of Thay, and the head of the Red Wizards that have not fled or rebelled against his rule. Famously once a member of a council of eight zulkirs that ruled over Thay, namely the Zulkir of Necromancy, about 100 years ago Szass Tam instigated a series of events that saw the end of his rivals and his rise to total power. Since that happened, Tam has partly recreated the state in his own image – Thay is now hosts the highest population of undead in the world. He is rumoured to be the most powerful master of the arcane magic that has ever lived.
Szass Tam follows a policy of ruthless annihilation of any Red Wizards and Thayans that dare to oppose his rule, and even those who simply flee it. He directly threatened Rath Modar for his attempted insurrection just before the Red Wizard was killed at Skyreach Castle.