The fall of Zigur
From Tales of Maj'Eyal
This quest is started by the Grand Corruptor, who will offer it to you during battle with him if you have at least 10 spells (or spell abilities), have not already visited Zigur, and when you bring him to 1/2 total life.
He will offer to let you destroy Zigur in turn for knowledge and power; he will reward you with the Corruption/Hexes; or increase your mastery of it by 0.2 if you already have it.
You will also be rewarded with the Anti-Antimagic! achievement.
