Greater Rifts in Diablo III are unforgiving sometimes—not because they're hard, but because you have 15 minutes to kill a huge amount of monsters, even if the dungeon doesn't actually have that many of them. YouTuber avtorouc entered one of these dungeons where the monster density was, well, quite low.
He was lucky it wasn't a huge, linear cave.
Diablo 3 - Near empty Greater Rift level [YouTube]
To contact the author of this post, write to: firstname.lastname@example.org