Started playing this last week. I'm through Anor Londo and Blighttown. Dark feels much more fantasy, while Demon's felt more gritty, dark and oppressive.

From what I've dabbled and read about the covenants, though, Dark's got the edge in RPG stuffs. Demon's had cool bits of backstory and stuff to be found in the game world, but Dark probably has 100 times that.

The backstabbing done by invaders is just beyond stupid, though. It was pretty bad and glitchy in Demon's, but it's flat out embarrassing in Dark.

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Anti-State, Anti-War, Pro-Market