Qou's area was filled with Demons and Fiends. The only humans that were in his area were servants and you can imagine what their lives were like. He knew that Havok was a child of darkness and knew full well how dangerous they were, but he figured that having Havok work underneath him would give him a lethal weapon to wield.
If the recruitment failed then he obviously had other options to fall back on, so one way or another he was determined to get Havok under his control.
Most children of darkness were snuffed out in their infancy, but now that one had fallen into his lap, he wanted to get control of it before it got killed.
Havok also knew what clan Qou was from and there was no better vessel for someone in his clan other than a child of darkness. In fact, it was the ideal vessel, even if someone offered him the body of a stronger ranker Qou would refuse.
