And no human civilization has ever come to an end.
To the best of my knowledge, not as a result of dealing with infernal powers.
You just basically described the standard fantasy elf or dwarf, but instead of brooding about orcs and ruined cities it was bad magic and ruined cities.
I think there's a difference between brooding about orcs - which are an external threat to a dwarf or elf - and brooding about the failings of your own people that caused your downfall. A closer example in mainstream fantasy might be the sons of Feanor Maedhros and Maglor.
Further, (the part you omitted) given their infernal heritage/bloodline, they would have unique insight into the culture and individual mind of the duergar. There would be a natural kinship in their exile...something of a Stockholm Syndrome relative to the greater culture...even if the two races/cultures are aesthetically different and governed by an opposing moral hierarchy.
This is more-or-less how it played out in my game, yes.
The PCs have dealt with the duergar twice - once earlier in the campaign to redeem some slaves that the duergar had purchased from a hobgoblin slaving ring, and then in the last few sessions - impressed by the PCs' prowess, and also the ability of the PC invoker to wield the Sceptre of Law (= Rod of Seven Parts), of which the duergar themselves possess one piece, the duergar have given the PCs shelter in their hold. The tiefling and the invoker (who serves, among other gods, Bane and Erathis) get on well with the duergar, though the tiefling also has a certain distance from them due to his sense that they don't understand their own tragic situation.
The party also has a dwarf PC - a fighter-cleric of Moradin - as well as the drow and an elf ranger-cleric, and the relationship to the duergar of the dwarf (who has to tolerate constant jibes at the inadequacy of Moradin as a protector of the dwarves) and the chaos drow (who is, rightly, seen as a threat to the order that the duergar uphold) is very different from that of the tiefling and invoker.
No doubt interesting brooding PCs who are dwarves, elves and humans can be created - and I've GMed some of them over the years! - but the tiefling origin story introduces a distinctive thematic element.
So basically DRIZZT took caster levels instead of ranger ones? Why wouldnt that work with a regular elf who wanted to unite the elf race and purge elemental chaos?
Maybe it would, but it would be a different PC. For example, the elf you describe probably wouldn't be an exile. S/he wouldn't have to be a member of a secret society, because s/he could probably be open about his/her goals. And there would not be the same relationship with Lolth and the Abyss.
As I'm certain you know, a typical Drow society is (dis)organized around a Lolth-centric regime. Worshiping Corellon would, of course, be as heretical as anything you could do. Reuniting elvenkind into a singular people again is clearly this characters primary motivation/quest.
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Purging the Elemental Chaos of the Abyss is likely an idea borne of self-interest as much as anything else.
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If demons have access to the Elemental Chaos by way of the Abyss, he leaves a potential opening for retribution every time his bloodline activates its sorcerous power.
The bit about heresy is certainly right. It fits with the general persona of the PC (he is also the party Bluff-bot, and notorious for dropping his Cloud of Darkness in combat without full regard to the welfare of his fellow party members).
The relationship to the Elemental Chaos is still being explored. The PC certainly wants its power, but is also interested in the idea and importance of change and transformation. I think it is likely that, downstream in the campaign, there may be conflicts between this PC and the invoker of Erathis.
Essentially they took basic fantasy tropes and found some excuse why they needed kewl powerz in order to play them.
Huh? All races in 4e have access to racial abilities. And tieflings are generally regarded as one of the weaker racial choices, as best I have a sense of the optimisation boards.
its quite easy to see how each aspect of these PC builds and their corresponding thematic color and agenda fit together. I know nothing about pemerton's campaign and I can throw that together completely off the cuff at a moment's notice. And it has nothing to do with "munchkinism" as any choice they make is just as powerful as the one they do not choose (given 4e's balance amoung build choices).
As I've indicated, you're pretty much on target with your diagnoses. I've never claimed that the thematic material in my game is particularly surprising or unpredictable! - I follow the standard fantasy tropes pretty closely - but I can't see any connection to munckinism. These are completely legitimate PCs that are interesting in play. And
interesting in play is my number-one criterion for a well-built PC.
And that half elf would suck too, but for entirely mechanical reasons. I.E. it would just suck at everything.
There is nothing particularly sucky about 4e half-elves, but the PC was a feylock, which is a hard class to play well. Hence at 3rd level, when the PC died, the player brought in the drow sorcerer in its place.
Klingons are fine for sci-fi. Not for D&D.
I think you may have missed [MENTION=6680305]technoextreme[/MENTION]'s point, which was that Klingons aren't a
sci-fi archetype at all. They are a fantasy archetype - the brutal but honourable warrior culture - with the thinnest veneer of sci-fi painted over them. (Other examples of this sort of sci-fi veneer over fantasy include the Fremen in Dune, the Hawkmen in Flash Gordon, the Jedi in Star Wars and Cthulhu in the HPL short story.)