Right now, I'm a young women that was falsely accused of a crime her assassin father commited and, for years, was abused in the prison by Adamus Phillida, effectively turning her into a broken human being. Shortly after being given freedom after the whole Uriel Septim spiel at the beginning of the game, she sought refuge in a cave but encountered vampires. She narrowly escaped death, but was stricken with vampirism, further warping her mind.
So now she's (understandably) a serial killer that does things to her victims that I'll not mention here after killing them and capturing their souls with a black soul gem. I originally intended to simply keep them as black soul gems, but I couldn't name them individually with the command console, so I decided to just take the shoes of each of my victims and then enchant them with their soul and just name it "[victim's name]'s soul," thus ensuring that her victims remain a part of her forever. She then keeps each trophy from every kill by placing the pairs of shoes on a shelf in the Vile Lair. I also use the command console to add a human heart to my inventory after every murder, pretending that she cut the person open and took his or her heart as a keepsake to be eaten later in the comfort of the home formerly used by her recently deceased father.
I justified her skills in stealth and murder by coming up with a story about how her loving assassin father taught her those skills. It just seemed silly that she would be able to do so well in the Dark Brotherhood, plus not get caught killing (I think) over sixty people by now. You know, I don't know why I bothered to type all this out. Still, it was fun just to share the twisted [censored] I like to do in my game.
So, yeah, I like to play evil characters.