I'm not convinced that either of those last two sentences are consistently true, alone or in combination.
I think lore often comes first, and suggests rules interactions (if any are needed - but see my previous post) that might arise from it. And
role-playing games, by their nature, frequently produce experiences independent of rules systems; I don't think I'm that unusual in having lots of occasions that my players interact with the lore of the setting in ways that aren't directly affected by numbers and dice!
The rules are not just "numbers and dice," though. Rules also include things like the DM describing what happens in the world as a result of the PC's actions, or the hair color of drow elves.
I regret to tell you that this example is one that I feel makes my point more than yours.
If they're the same wizard, the
only thing that sets them apart is lore, independent of rules.
(But I also disagree that they're not different in flavor - the tropes and feel of those two settings suggest that they'd be pretty distinct. I would go so far as to say that you could take the same character sheet and put it in the hands of two players -
skilled players, mind - who are immersed in the lore of the two respective settings, and you'd get two very different experiences out of them. Which is to say that lore matters - of course it does! - but not always in a definably mechanical way.)
If a setting has "tropes" that one should use when creating a character in that setting, that's also a rule. In D&D, these tropes are typically telegraphed through character creation options like race, class, background, etc.
No argument there! Of course a defiler wizard tells a different story; that's a very clear case where lore and rules are so neatly married as to be well-nigh indistinguishable. But consider two things, or perhaps the same thing from two angles:
1. An arcane spellcaster who draws on the life-force of nearby creatures isn't so closely, uniquely married to the lore of Athas that you couldn't use that idea and its attendant mechanics in another setting; and
2. When you start with the lore that "this type of caster must drain the life out of other beings to fule their magic," you wouldn't necessarily and inevitably wind up with the exact mechanics that have been used in DS in its couple of editions. I can think of several ways you could model that in 5e, and I bet you can too. Which is why I hold that rules and lore are indeed closely related, but not quite the same thing.
1. Like I said, it's easy to allow anyone else to use the defiling rules, but outside of the other rules for playing a Dark Sun character, you'd be having a distinct experience from a "real" defiler.
2. Different mechanics create different experiences.
For instance, the 4e defiling mechanic created a "temptation of power" experience - you always had the option to defile, each time you cast, but you never had to take it. The 2e defiling mechanic served the experience of defining your entire character by whether or not they defiled. Once you decided what kind of character you wanted to play, you were largely defined by that for the reset of that character's existence. This meant that the experience of playing a defiler in 4e was largely one of a recurring question about violating nature (and your allies) or not, while the experience of playing a defiler in 2e was largely one of defining yourself
as a defiler and creating a character who would ruin nature who might nonetheless be a heroic character in Dark Sun, thus emphasizing themes of dark and flawed heroes in a dark and flawed world.
The main question there is "
does this mechanic deliver the experience the player should have?" If you want your player to have the experience of actually killing the land to cast their magic, the 2e mechanic will give you that more and more often than the 4e mechanic (where the player is likely to rarely - if ever - actually defile). But, if you want to emphasize the evil of the sorcerer-kings, the 4e mechanic might do a bit better in delivering that experience, since it is such a rarely-used option: the sorcerer-kings must be
truly wicked, since they clearly disregarded the safety of their own companions!
When designing any other mechanic to represent defiling, this is how you evaluate if it's "good" or not: you evaluate how well the experience your mechanic creates lines up with the experience you
want to create. So while many mechanics could hypothetically represent defiling, not all of those mechanics are equal in producing the experience of being a defiler - only those rules that get you to the lore are actually good rules for that lore.
