Like a blur, Siwon sprung forward, acting on both his body's own quick response as well as from the premonitions his demon had given him moments ago. Perhaps it was right to state that failing to perform this morning's ritual lead to such an ambush. In the end, it didn't matter. What mattered now was to act, and act quickly.
Leaping away at speeds fast enough to leave an afterimage, Siwon seemingly absconded from the group and rejecting the fate of death. He was no hero, and would likely stumble or hesitate in fear if he tried to save the mage or the priestess, adding yet another untimely demise to the brazen boulder. If anything, should he decide to flee, it's likely he'd find his way back to civilization once again, likely without a guilty conscience due to his calloused behavior. As a matter of fact, every bone in his body screamed at the Fiend Knight to cut his losses and run.
And so the Fiend Knight ran, speeding towards the eastern hillside until he reached an incline low enough to sprint upward, close to the boulder-chucking beast. Trusting in the strength of his legs, conditioned by his training, the Fiend Knight swiftly scaled the hills in an attempt to flank the monster before it could throw another rock, his spear pointed towards where its ribs should be. Siwon knew he had to draw its attention away from the rest of the party so they wouldn't face the threat of a ranged adversary any longer, and he could only hope that its initial targets would find their way out of harm's reach.