DA:O? Toss up between Ariane, Shianni, and Lanaya, tbh. Well, if we're just talking about looks, that is. Oh, and Iona.
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DA2? Hmm... Merrill's too innocent to be attractive, imo. If she was more matured emotionally I'd probably say her. Hmm... most of the elves looked kind of weird in DA2, so this is tricky. ... I guess I'd say the elf you have to talk to in A Murder of Crows in Act III. I forget her name...
Oh, wait, that's right. Her name's Variel.
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Oh, and Mithra too.
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EDIT: Crap, I forgot about Tallis! D:
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Though none of the elves in DA2 top Bethany, imo.
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Not that I wouldn't mind one of the elves I mentioned above being on top of Bethany * gets slapped by Bethany * ..... yeah, I guess I deserved that, but it was worth it because now my mind has taken that scenario and ran with it. Ah, the benefits of having a dirty mind.