My party and I are in a city who's king was just killed. There are three offspring of the king. One doesn't want to rule, one only wants to because her father did, and the other is missing. There is this necklace that we have to destroy, that can only be destroyed with this holy weapon. Right now, the only one able to wield it is the one of the offspring the one who wants to rule. The city will be attacked if it is left without a monarch. So my character feels that the only way is to take the sword. She is a tiefling rogue and with sleight of hand could easily take it. Her father was full-blooded elf and her mother was half-fiend half-elf. There is not an evil bone in my character's body. All my DM will tell me is that the sword is gladly offered, but that the sword has detrimental effects to anyone with demonic blood. So if I try and take it and don't succeed something will happen, and If I succeed something will happen. This is edition 5.