For someone as quick-minded as Remy, everything had happened so suddenly, beyond his comprehension. For once, his mouth was shut, having no words to describe what just happened. He sat on the ground cross-legged, just staring down at the stony floor. He took another moment to look at his metal arm, slowly making a fist. He let out an anger-ridden yell, something this optimist was unaccustomed to doing. The Breton punched the ground repeatedly in frustration, and rightfully so. He just stood back, frozen in awe of the situation while his friends risked their lives taking on the man he was openly willing to allow to join. If he couldn't think on his feet on this occasion against some random vampire, what chance did he stand against a dragonborn? His inability to participate didn't allow him to aid his friends in freeing Seryn when they all needed it most, and forced Arngeir to resort to the final-most plausible means of ridding the beast from this location.
He stopped beating down on the poor ground and looked to the others. His gaze met the coping Anya, a dazed Irelius, a recovering Virk, and a distraught Roggvar. He stared back at the ground, feeling he couldn't look them in the eye. He still spoke to them, but in a tone much more subtle and slower-paced than his usual voice. "I... I'm sorry, friends. For that I truly am." Still with his head down, he pick himself up off the ground and slowly made his way to his set-up on the other end of the cave.
He took out a notepad and some charcoal, jotting down all the range of factors and environmental aspects that could have kept him from doing something in that fight. The more he wrote, the more paper would end up on the floor as he scribbled out each possibility, tore the pages, and had strewn them about. Remy believed that science could solve any riddle, unlock any puzzle put in front of him. Unfortunately for him, science had no place in his personal conflict. He was genuinely afraid, and no dwarven machinery or alchemical alembic could ever mask that.