"I think just getting the bag should be safe enough, but let me ask Skate a question or two before you go out there. Is there a light source around either corpse? I fallen torch or lantern?"
"Maybe the traps we've encountered and the corpses here are gettting to me. It would be logical for the people here to use light this deep underground. If they didn't then perhaps there is a good reason not too. I thought perhaps the light was causing the melting earlier. I wouldn't want it to trigger something else here. Given our crispy friend I'm loath to use the braziers, but I would be curious if they appear to have been used recently."
The braziers would be a logical source of light. The char on the floor and the burns on Sorden's arms appear to emanate not from the braziers but from the brick he's holding, which is partially inserted into the hole in the floor in front of the portal (which appears to be sized to fit the brick).
The party moves to the area of the altar and the portal (DM decision, since that seems to be where the action is. I'll go ahead and reveal that no traps will be set off merely by being in the area . . . ).
IC:
"There was something . . . a brick in the hearth of the Wickshine's Last Inn . . . it disappeared the night of the attack. Illé Sorden must have taken it with him when he fled the inn during the attack."
OCC - Mike, I don't remember a brick disappearing at the Wickinshire, was this common knowledge? Maybe I just forgot, I am nearly as old as you, Mr almost 40.