Dedicated Dark Souls player The_Happy_Hobbit has done the unthinkable and completed From Software's notoriously challenging action-RPG without taking a single hit.
The successful run takes approximately 4.5 hours in which The_Happy_Hobbit doesn't block with a shield, use magic, or implement any glitches to skip sections of the game. The run begins at the 29-minute mark and ends at approximately four hours and 58 minutes.
As detailed on Reddit, environmental damage is allowed, but only if it's not cause by an enemy's attack. So some late-game section where you need to run through lava will obviously chip away at your health, but stepping into a pool of lava vomited by a boss is against the rules.
The closest thing The_Happy_Hobbit does towards cheating is exiting the game on rare occasion when things get too hairy and he wants another shot before taking damage and forfeiting the entire run. For example, the runner bails at the fight with The Four Kings when too many of them spawn at once and start tossing homing projectiles.
So what's next for this most hardcore of hollows? Currently The_Happy_Hobbit is attempting a run wherein he slays every optional boss (including those in the DLC) while staying true to this unforgiving ruleset. You can watch his streams on Twitch.