Originally Posted by Draconi Redfir
Or C: Both of Duv's parents were Goblin, and Malgubliyet, a celestial being as a god, blessed their child with a portion of his own divine powers so she may lead the goblin people as the chosen one.
I'm unsure if you're familiar with how the term 'celestial' is defined in the D&D cosmos (and the one Thunt is using, for that matter), but that's not precisely how it works.
To speak in general terms, planes in D&D are classified as Material (that's the one we live on), Transitive (Astral, Ethereal, and Shadow planes), Inner planes (Fire, Water, Earth, Air, Positive Energy, Negative Energy, Demi-Elemental, Quasi-Elemental), and Outer Planes which are further subdivided into Upper Planes (the [Good]-aligned ones), Middle Planes (neither good nor evil) and the Lower Planes (the [Evil]-aligned ones).
Now, a being from one of the Upper Planes that's not an enhanced animal or a Petitioner (that is, a dead person) is known as a Celestial. They all share the inherent quality of being physically composed, in some part, of pure goodness.
A being from the Lower Planes that is not an enhanced animal or a Petitioner (that is, again, a dead person) is known as a Fiend. Fiends all share the inherent quality of being physically composed, in some part, of pure evil.
Malgubliyet and other evil-aligned gods are all technically Fiends, though the whole 'being a god' thing takes precedence. His residence on Acheron (Law tainted by evil) marks him as a denizen of the Lower Planes; no part of his nature is 'celestial' and indeed anything to do with Celestials is anathema to him. The half-celestial template, bestowed on Duv, would give her powers entirely
suited to destroying evil, with such examples as Malgubliyet's entire church and most of Goblinkind. In addition to being crowd-unsafe from the goblins' point of view, this would also actually harm Duv herself if she was evil - it's crowd-unsafe for her, too.
Meanwhile, Half-Fiend powers are very good at destroying Good, and are crowd-safe for goblins, causing it to make more sense all around.
However, there are some other options for what template she might have. Aside from Thunt!Template, she may be a Winged creature (though that seems a little passe), or she might be a God-Blooded creature (though why she'd have wings at that point is a total mystery). All of those options remain open and would make sense. It's just that there is no way in any flaming hell that Half-Celestial would.