Not D&D, but Pathfinder -

My drow girl is the bastard daughter of the previous Emporer and a local prostitute. While her mother was made to disappear once my birth was discovered, the Empress was merciful to me and allowed me to live and train as a soldier, as long as I agreed to forsake any claims to any lands or titles. I accelled in training.

200 years later, she's now the former captain of the empire's army and former personal protector and basically older sister/ mother figure of the now-empress. Once while out in secret with the then princess, she fought off assassins that tried to kill the princess. She was successful, but took near mortal wounds in the process. Thanks to being so high ranking, she was immediately given the best care one can receive, though she was still left wounded enough that she would need time to fully recover, and was to spend a few weeks in a hospital in town.

Meanwhile, another player's character, whose role in society is to provide mercy to those suffering, came into the same hospital. He was there to give a merciful end to someone else, but due to some sort of mix up in paperwork, he ended up killing me instead while I slept.

My character's soul was pissed. She had survived over 200 years of combat and assassination attempts (elves) just to get killed by some low ranking priest that made a mistake. So, some entity that was holding my soul offered me a deal - agree to kill the priest who killed me and I'd be resurrected. I agreed.

She returned in her coffin in a mausoleum outside the city, already having started decaying, though it seemed to be stable. When she return****ed to the palace, they denied her entry, not believing her story due to me having been dead for 6 months. So, I decided to start investigating the priest, who had been let go once it was made clear that an honest mistake had been made. Turns out he was nearly across the continent on his mission trip, so my penniless character lived out in the woods, made friends with a bear, and waited 8 years for the priest to return.

Once he did, I sat down and forced him to talk. 8 years having passed, she found difficulty in remaining as angry as she had before, and something in her snapped. She decided to forsake the deal she had made, instead making a rash decision to instead help her murderer in his mission.

Almost immediately, she began rotting again. We start the campaign in a few weeks after having wrapped up one that went for 5 and a half years last week!

Hope that all made sense. It's hard to summarize the like 7 pages of lore I sent my DM into a single comment.