Ever since what happened in the mountains and how Lu disclosed his ability to control the monsters and Cane suspected it was actually him, who had summoned the monsters to the palace, though the lycan was adamant it was not him who had instigated it, Cane had been trying to practice controlling his ability.
But, every time he did it, black wisp managed to emerge from him. As this ability belonged to the lycan, it was only right for this creature to come along when he tried to use it, which didn't help if they were attacked by monsters and were surrounded by people, who were still not aware that Cane was the lycan.
However, Cane was willing to risk everything when he watched in horror that Iris was in a dire situation and Lil Thing wouldn't last long.