Another log on the fire

Nemon put a torch near the bars. He almost lost his arm, when a huge claw made a swipe for him.
"Weasel", said Gruffydd. The group gave a collective shutter. They had witnessed the death of Dimzad, a former member of the group, to a giant weasel. They still remembered the lower of half of the dwarf's body walking around, spurting blood. The top half devoured by a weasel just like this one.
Everyone began notching arrows.
"You're not going to simply kill a caged animal?" Morey the young magician asked, horror in his voice. "It can't hurt us, locked away like that".
Just the then the giant lunged at the cage. The rusty bars gave way in a few spots.
"Shoot it! Shoot it!" Morey screamed.
It took way more arrows than anyone had hoped. The cage opened, Gruffydd rummaged through the cage. He was, like the rest of the party, already covered in blood, dirt, and soot. What was a little weasel crap too? He found a few undigested coins and a belt buckle. Probably from some hapless adventurer.
Miss Adventure yawned, "We should leave. It's getting late, and this level is empty."
"No it's not", came the retort from the cleric Gustav. "we still have that room full of baby dragons."
No one seemed interested in the room.
"Look", said Gruffydd. "I'm gonna find some other way out of this place that doesn't require me hauling my ass up that rope to the top of the well. Who's with me?"
The group began shuffling towards the door and to the stairs to the level above.
Nemon, the tough mercenary from the wars in the South, took pity on the young holy-man. "I'll go with you".
With the rest of the party waiting to move on, Nemon and Gustav made their way down the dark corridor to the doorway plugged up with the filthy divan. Nemon stood back a ways as Gustav clambered up the side.
He peered in. Still dark, except for the occasional flash on light, and the soft clicking that proceeded it. He held on with one had, while he rummaged through a bag. He pulled out a flask on torch oil. Then Gustav threw the flask through the small gap between the sofa and the top of the doorway. He heard the flask break.
Click-click. Nothing. Click-click.
"BOOOOOOM!"
There was a flash of light and an impact. The group down the hallway felt the concussion and the heat. Nemon was knocked off his feet. Gustav disappeared under the burning wreck of the divan.
The hall was engulfed in fire.
And movement. A least a dozen beetles, the size of large dogs, came pouring out of the room. Fire spitting out of their mouths...