Nothing inside?

Ethan watched as the seventh pile of rat bodies grew taller, nearly reaching his waist. The overwhelming stench of blood and decay saturated the air. Even Lia, who had been diligently buffing his minions without complaint, wrinkled her nose in mild disgust.

Ethan, however, was still grinning. He hadn't expected this job to be such a gold mine. His minions had been leveling rapidly, and he was getting closer and closer to finally stepping over that first barrier and crossing into E rank.

"Just a bit more," Ethan murmured, his eyes locked on the gaping tunnel in the ground. The number of rats coming out of that hole was ridiculous. 

Just what was inside that tunnel? This was way beyond a simple infestation. This tunnel felt endless. No matter how many they killed, the tide of creatures didn't slow.