Description
The energy radiating from the zombies is the same we faced when the Ward fractured! Only a powerful mage or relic could generate such energy. My Scepter of Cleansing can neutralize the magic, but you must use it at the source of the contamination.
Upon completion
So, the source of corruption was a crystal in the crypt's final chamber? That's the resting place of Targan Graysward, the former owner of the Deepstrike mining operation. He died not long after the undead appeared.