One of the major issues with using the Demon tier amulet was that Quinn was unable to see through the eyes of those that were Marked, while also seeing through his own vision. He could switch who he had full control over and then see from that person's point of view, but not all of the Marked visions were shared.
This meant Quinn didn't know what Vincent was currently doing, and neither did Vincent. Still, they both knew where the other was and what they were attempting to do. Which was why Vincent never expected such a vast amount of energy to leave his body.
At first, it was gradual, but the fighting was over in the Shelter, so Vincent wasn't really worrying too much. He put on a brave face and ignored it, counting to act as he had been doing. However, soon the energy started to ramp up, so much so until his legs felt like jelly.