Don't have to kill
Something that Quinn had to keep reminding himself as he went to face the Dragon, was that his goal in this fight wasn't to defeat it, just to buy time. It was a foreign feeling, when faced with a beast, but eventually it had gotten through to him.
It was why he had opted to land on the giant beast's back, allowing him to hold onto its scales as it struggled. As a Vampire Lord his grip strength was enough to withstand the Dragon's efforts of shaking him off, yet given the hardness of its scales it was also almost impossible for Quinn to do the beast any real damage, but he didn't need to.
All he needed to do was distract the beast while the tree did its job.
Using this opportunity to his advantage and remembering what he had done to the Dragon before, Quinn wickedly used the active skill in his gauntlet.