What kind of rules could there be for rape anyway? Sure it deals considerable psycological damage, but there is no mechanic to represent that in D&D anyway, even if you did for some reason want to put in into your campaign. It would be reflected only in role-playing that NPC/PC.
The closest we got in my campaign was when the characters defeated an evil wizard, they found a woman, naked and bruised, tied up in his bed. They healed and freed her, and continued their quest. There was no reason to go into greater detail than that.
edit: it hadn't occured to me that they might get "powers." That certainly wouldn't happen IMC.