A boss... not to mention an ugly attack that kills half your HP in one go. I usually drag a huge train in the Abyss when I'm on my way out (always taking up the big room cause no one is around)... and then I'd see this one person just standing around at the entrance thinking no one would be running for their lives with little to no HP stones.
What I don't like is when they see that I'm dragging a train behind me and they don't even bother to at least get out of the way. I don't want to kill people so I stop but they don't move...
Next time I'm just going to exit the dungeon.