As the source of the Auras, William obviously didn't have a good understanding of what his opponents felt when they came into contact with it. He only knew that it was strong.
Seeing thirty-eight unconscious peak Cultivators and a shivering Anula, William finally realized just how much impact his Elements had on the mental state of a person. He was thankful that the Heavens didn't see the remainder of his Elements, lest he add more troubles to his list.
"So much for your intricate plan." William walked up to Anula and suppressed her movements with the Territory of Sealing. With her and the remaining Tribulation Transcendence Cultivators, William transformed into the Poison Elemental Form and touched each of them with the Soul-Sapping Necrotoxin.
With fine control of the Poison and Life Elements, William kept each of his targets alive while slowly stealing their Soul Strength. As long as they had a little bit left, they could still survive, but all the extras would belong to him!