Boundary landed beside Dante and the demon he fought against, he sensed that the angel was injured and that he needed some help, he held a gun in his hand probably to defend himself. Seeing as Boundary did not like demons, helping the angel seemed like the better choice of sides to pick. He held out his hand and chanted one word, "Umbra!" a blast of darkness shot forth from the palm of his hand and collided with the demoness, the recoil caused Boundary to slide back only slightly.