It's a good question: Mithrun is likely not looking good. With another Devourer dead, Mithrun shakes himself, as though doing so could dislodge the piercing pain in his skull or the fog threatening to settle over him. Both just inconveniences, in his estimation--

--Unlike the sudden approach of something.

Mithrun doesn't exactly hear what Cloud says - some sort of sound, dulled under the thrumming of Mithrun's own pulse in his ears. He does hear the crunch of snow-- a moment's warning, in his mind, of a potential threat. He rounds on Cloud, his fangs snapping down onto flesh. It's barely even a choice - just on-edge reflex, a burst of instinct at the wrong moment.

For whatever it's worth, he doesn't stay clamped down long; the mistake clicks an instant after he bites down, and Mithrun jerks back, startling.