The League of Magic, better known simply as The League, is a group of the most powerful magic-users known to man.
The League is an independent agency beholden to neither The Empire or any other governmental body - truly not even all the members of The League even live within The Empire's jurisdiction. The League's purposes and activities are known solely to them, and few people even know of it's existence.
After the Fall of Korhal, the League had a meeting and discussed what to do about the problem of the Witch and the Horde. After a long discussion and vote it was decided that the League would not try to fight her, in an attempt to not draw her attention to them and slide in under the radar as it were. In essence it became every man for himself. This was their downfall, as the Witch tracked hunted each of the members of The League.
Ulrezaj's died at the hands of the party. Aldaris died at the hands of the Witch. Abathur served her for a time but then later died at the hands of a curse bestowed on him by the Witch. Eddie Izzard vanished from existence. The remaining members died at the hands of the armies of the Horde.
There are no surviving members of The League.