Killian puts his rope away and starts swinging with his spiked chain and manages to start to get some of the debris that way...but it will be a few rounds before you get enough to climb on.
The bars of the iron grate that separate this room with the one above look wide enough where you might, if you were lucky, be able to geta grapling hook in it.
By the way...looking up there you manage to see the two goblins who fell unconsious due to Az's spell, get up. Also the goblins across the pit..look a little less stunned, and start to goto the pair of doors on the far wall.
You can't take 20 when there are enemies around. Threats and distractions.
Actions?