Vespers host easily imo Hardest but highly engaging and fun to play, best atmosphere, experimental bosses, sweet loot for its time including the exotic. I love the variation on the DSC mechanic. I have never found solo flawless dungeons super challenging but this one was an absolute grind and so much fun to go for, ended up doing it twice. I will say I dont find it as fun in the new sandbox, but in heresy with that sandbox and artifact, I could run it all day every day (and did, my buddy and I would run carries on fireteam finder when we were bored) Honourable mentions - I was impressed by equilibrium, but found the mechanics tedious, way too much running around and waiting and it loses me fast. But some of the best dungeon loot ever hands down, sweet atmosphere, cool and unique encounters. I like sundered doctrine a lot, knocked it out of the park with the atmosphere and I love the core mechanic. But find it boring to run repeatedly, takes a lot of time to learn how to speed up things like the first encounter and the worm door and im just not bothered with it. I absolutely loved running ultimatum rite of the nine ghosts of the deep and spire. The things they "fixed" about ghosts are amazing and its criminal that they werent just patched into the version you can play now. I dont mind the swimming that much. These dungeons are just kinda boring on normal difficulty imo, the challenge was what made them fun.