Sewer Prison

I was picturing much smaller stairs.
Tethrik grabs Blackwall and runs up the stairs. Once he reaches the top, he'll set the man down. "Come to think of it, what's so important about you that I am being paid to bust you out?"

Into the Dungeon

Tethrik goes to the nearest closed sarcophagus and presses his rifle up against the stone right where the head would be in order to shoot a hole in the lid. Better to see what's inside before opening it. Could be a mummy or another undead monster.