A monster comes out and attacks

“Alright,” River said. “As you draw near to the cave, you get a better look at it. The entrance itself is a large hole in the ground, right at the base of one of the bigger hills. It looks like it goes downward into the ground at a steep angle, forming a ramped tunnel of sorts into darkness.”

“I have darkvision,” Tess said immediately.

“...Right, of course,” River said with a sigh. “Regardless, with the angle it goes down at, you won’t be able to see very far unless you’re right up at the entrance.”

“Hmm, alright, I’ll go right up. But can I try to be stealthy about it?”

“Sure! Roll me a stealth check.”

Tess tossed her die. It turned up a one. Nissa, sitting near enough to see the result, made a sympathetic noise. As a rogue, Calith’s stealth skill was high—but not high enough to turn that into more than a nine.

Grinning evilly, River said, “Well… you continue to approach the cave. With your streets-honed skills, you’re able to stay quiet right up until you make it to the mouth—when you trod on something, which snaps loudly underfoot. Glancing down, you realize… it’s a bone. Your eyes then rise, and with your darkvision can see that the tunnel going downward is littered with bones, scraps of clothing, and bits of wood.”

Tess grimaced. “Shit, umm… okay, I slowly start to back away, hoping that whatever’s clearly living in there didn’t hear that.”

River rolled some dice behind his DM screen, then shook his head and announced. “Too little too late. As you back away, a bloodcurdling roar erupts from the cave, and you see a dark shape suddenly begin to charge into view. As it barrels toward you, you can see that it’s a—”