Sarah

Sarah was Nick's wife.

Background
Not much is known about her, except that somewhere in time she married Nick and had a son. Somewhere before Season 5 started and Season 4 ended, Sarah and her son were murdered during a house break-in.

In 2009, Nick (still in grief for both his wife and son deaths) was haunted by hallucinations of her (actually Lucifer, who has just being released from his cage), trying to convince him into becoming his vessel.

Lucifer (using Sarah's shape) finally convinces Nick by saying:
 * Lucifer: You people misunderstand me. You call me "Satan" and "devil", but... Do you know my crime? I loved God too much. And for that, he betrayed me—punished me. Just as he's punished you. After all, how could God stand idly by while that man broke into your home and butchered your family in their beds?
 * Lucifer: There are only two rational answers, Nick—either he's sadistic, or he simply doesn't care. You're angry. You have every right to be angry. I am angry, too. That's why I want to find him—hold him accountable for his actions. Just because he created us doesn't mean he can toy with us, like playthings.
 * Nick: If I help you...can you bring back my family?
 * Lucifer: I'm sorry. I can't. But I can give you the next best thing. God did this to you, Nick. And I can give you justice. Peace.
 * Nick: How do I know you're telling the truth?
 * Lucifer: Because, contrary to popular belief, I don't lie. I don't need to. What I need...is you. Nick, I need you to say yes.
 * Nick: Then yes.