Is this sentence correctly structured and worded?

FYI- Yaphyll is the diviner, Szass Tam is the lich, and the Council is the other mage-lords. Yaphyll then had a vision of an imminent catastrophic event, the Spellplague, and gave Szass Tam a cryptic warning before she was surrounded by blue flame and broke free of the undead wizard’s control. When he tried to regain power over the diviner, Szass Tam unintentionally killed her with his poisonous touch. Following Yaphyll’s death, the lich began planning his campaign against the Keep of Sorrows and decided to lure the Council’s legions into his trap by using Hezass Nymar, the tharchion (governor) of Lapendrar and the Eternal Flame of the temple of Kossuth in the city of Escalant, whom he knew was going to soon betray him to the other mage-lords.