Lars, you fire off a heavy bolt at the stone door. Given the tight quarters of the space and the number of your friends around, they have to press against the walls lest they be skewered by your shot. The bolt strikes the door with a loud crack and it splinters into a few pieces. The door and the runes are unaffected.
Kirio laughs out loud and winks at Lars "That was... entertaining, if rash, love it!"
"Alright, well, I doubt Hrimr will find traps, but I think he has the right idea... let's have a better look around shall we?"
Kirio begins methodically searching the room for anything else unusual, eventually joining Hrimr at the door, looking for any handle or mechanical means of opening it...
Kirio, you do not see anything of interest in the room. The door itself has recessed handle carved into the door that presumably would be used for opening the door.
Kirio then shrugs and begins crawling back through the dragon's mouth "well... if you can't cancel the Arcane Lock spell, let's maybe come back later I guess." he pause and looks at Hrimr "strangely aesthetically pleasing... your siluette in the light of those runes dwarf. Any strange stone shaping magic you have might... I don't know... melt or reshape that door?"
As soon as Kirio grabs the handle and heaves as if to open the door, the room is suddenly bathed in vibrant orange-red light. The door does not budge, but the runes flare angrily and a series of mechanical sounds clink, thud and crack ominously behind the walls and ceiling. You hear a sudden sound of stone sliding against stone from the ceiling. When you look up, you see that hundreds of small slots have opened in the stone ceiling and liquid hot magma begins to collect and then fall, raining down upon you in fiery globs. The lava lands on you in clumps, scorching your clothes, singing your hair and scalding your flesh. It collects on the floor and begins to collect, filling the room as water would.
GM:
I've updated the map (file is Fire Tomb 2.0). Lava has begun to rain down from the ceiling in this room. Every square is affected. Escape is possible back through the shaft, but since it is at head-height and has no hand or foot holds, it requires a DC 10 climb check to access. We are now on initiative. The trap went first (hence its placement as #1 on the initiative list).