I'd argue that Conan's world doesn't use D&D style hitpoints.
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Conan's world is more deadly than the typical D&D campaign as presented by today's version of the game.
I dunno.
How often does Conan die?
True, but Conan also has plot protection by virtue of being the main character of the book series.
That's because Conan has script immunity. Ask many of his adventuring comrades the same question and you'll get a lot of "No answer. He's dead."
Given how often Conan (and the pulp sword and sorcery tradition more generally) is cited as the inspiration for D&D, it would be odd if D&D in fact couldn't do Conan. (That's not an argument, obviously. Just an observation.)
If I wanted to run something Conan-esque in 4e, I would overwhelmingly use minions. And I would be prepared to narrate mechanical hits as fictional misses. I started
a thread about this a while ago. From "The Phoenix on the Sword":
The king took Ascalante's point in his left arm, and the outlaw barely saved his life by ducking and springing backward from the swinging ax. . . .
Ascalante leaped like a wolf, halted almost in midair with incredible quickness and fell prostrate to avoid the death which was hissing toward him. He frantically whirled his feet out of the way and rolled clear as Conan recovered from his missed blow and struck again. This time the ax sank inches deep into the polished floor close to Ascalante's revolving legs.
Clearly when Conan is stabbed by Ascalante, he has (in D&D terms) been hit and suffered hit point loss (perhaps he's been bloodied). But what about when Ascalante ducks and springs backward, then falls prostrate, and then whirls his feet out of the way? To get Conanesque 4e, you have to narrate that as hit point loss. Hit points become almost pure "plot protection." (Except perhaps for giant slugs and the like.)
Most NPCs and monsters would be minions, though, and so have no hit points - reflecting the fact that Conan has a better than 50% chance to cleave their skulls on an attack!
Conan most certainly does get seriously hurt and/or injured, and he is on death's door in multiple stories.
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I'd also say that Conan stories do not feature what D&D calls AC; to me, I'd say there are active defenses going on. Things such as parrying, blocking, and dodging out of the way (again, in my opinion) are much better fits for the style of story than AC. I feel that combat in Howard's stories -not just Conan, but Kull and Bran Mak Morn as well- is fluid and dynamic. There are actions and reactions happening quite often.
The dynamism and active defence I would do via liberal use of out-of-turn powers (like the duelist in Dark Sun, or the various ranger powers that allow a shift in response to being hit).
The permanent injury can't be done in by-the-book 4e. You would need to introduce conditions of some sort triggered by skill challenge failures, as a result of being dropped to 0 hp, etc.