With the fall of the Scarlet Crusade, their disguised demon leader, Balnazzar, released the possessed body of Grand Crusader Dathrohan and went on a rampage, killing every remaining crusader here. He then used his necromantic power to raise them all as vile undead slaves.
Balnazzar refers to his new army as the Risen. We cannot let him grow this army - they are extremely powerful and, unlike Arthas' Scourge, Balnazzar will not hold his forces back. Kill him while we still have a chance, <class>.