Warlock background questions

[Shotgunbunny]

Hellowdy, folks!

I'm working on a background for a Warlock character, but this is raising a few questions.
In short, the story I have so far is that the character, who's a young woman, was struck with an incurable skin disease that left her face all disfigured. So one of the reasons she makes a pact with a devil is to become SUPER EFFIN' SEXEH. She manages to contact the devil through an old infernal tome she finds. This poses some problems already though.

What sort of disease could cause an effect like that and not be curable...with all these demigod clerics prancing through the streets?
What level of devil (epic rhyme) would even bother to heed the summon of a teen girl?
Expanding on that, what deity would be proper for a Warlock? Asmodeus is supposed to be a selectable Deity according to the FRWiki, but apparently I can't pick him on BG. Although that made the most sense to me, as Deity and possibly as granter of thems powers. Does an archdevil not have the power to keep you from the fugue?

On the other hand, I'd like it if her contractor could be a devil of such power that she might one day be able to face off against him.

[DM Narshe]

Anything genetic won't be cured. Also, she could simply be an ugly duckling.

Imps are often the ones to offer pacts, though most others can as well.

[Shotgunbunny]

Also, she could simply be an ugly duckling.

I'm....not sure why I didn't think of that myself. XD

[DM Novus]

Please read this: http://bgtscc.net/viewtopic.php?f=49&t=30656