[He's instantly on guard as soon as he hears the sound, shifting into a defensive position, his hand already starting to glow with energy. He listens carefully for that sound again, a kind of slithering, scratching sound-- but it's hard to pinpoint where exactly in the tunnel it's coming from, how far down or how large the creature might be. But it's getting closer.
Shiro shifts a little, as if to direct Keith in some way, but he doesn't get a chance before something's launching itself out of the darkness and directly towards them with a loud shriek.]