"Wh- Holy shit!" Constans reflexively threw an arm over his face, turning in response to Bethen’s yelling just in time to see the massive spider bearing down upon him with bared fangs like fillet-knives. He lost control of the freezing spell he’d been brewing upon this sudden shock, a flurry of cold air whipping up around him violently and sending his robes flapping. Behind him the monstrous creature's brood skittered away, hissing and chittering angrily as they disappeared into shadows. In the awkward few seconds that ticked by after he failed to be mauled in the face, the apprentice glanced tentatively over his elbow. For this effort he received a mortifying eyeful of giant, toothed gullet, frozen mid-strike just inches away. He blinked away his shock and tore his eyes from the sight with some effort, backing away rapidly.
“Well, I guess you would believe the size of those spiders!” he joked, never able to take anything seriously; a slight quaver in his voice, though, betrayed him. Constans raised his hands as he quipped, aiming his palms at the vulnerable creature, the faintest red glow illuminating the shelves around him as the apprentice imagined flame; yet no inferno erupted from his fingers as realization trickled down icily through his mind. A faint sound from deep, deep in the tunnels passed over the threshold of his conscious awareness. It was a tapping, or a… thudding noise, something like someone softly beating on a drum, the thrumming growing gradually louder and faster- his eyes widened with horrified realization.
He threw his weight at the frozen spider instead, preserving his spellcasting energy by kicking viciously at several sets of delicate, frozen legs. The first one he’d never even heard coming at him until it was almost too late- how many of them would there have to be for them to make noise at all? A minute ago this whole thing had been a joke, but it was rapidly becoming a nightmare!
“Run for it!” He cried to Bethen, his foot shattering several limbs with a satisfying crack. “Do you hear that? There’s more of these things!”