There's a moment of surprise when they both pause to boggle at his Gestures. There's not actually any time to explain just now though, as the thing rallies and turns its focus to Camilla.

The guidance catches his attention and directs it toward the creature's spine, even if he doesn't know exactly what part of its spine they're referring to. He's not unintelligent, just new to dealing with human worlds. He calls back a "got it" before ducking low and rounding to the back of the construct to perform a similar Gesture to the one that had protected Camilla, only this one wraps the spine of the creature in a corrosive layer that starts to eat away at its vertebrae. It would reduce the amount of power that the thing could put into its strikes, albeit temporarily, and give him the chance to strike at that weakened place with his axe. It does a fairly substantial amount of damage, but likely not enough to destroy it outright.

Would he even gain any flesh from this thing when it fell? Would that matter here? Hm. Probably not.