Natasha "Sage" Spence is a recurring character in the sixth and final season of Gossip Girl. The daughter of Steven Spence, Sage enters into a relationship with Nate Archibald by telling him she is researching for a class at Columbia University. However, this is later revealed to be false, as she is actually attending Constance Billard School for Girls and is taking classes at Columbia on the side.
Before Serena met Sage, she thought Steven was sleeping with her and Nate, who was seeing Sage, thought the same thing. He breaks up with Sage, and Serena holds her suspicions of Steven inside until The Conservancy Gala that she's hosting. There, Steven reveals Sage to be his daughter and Nate finds out she's a minor, although they get back together anyway.
Sage always had a grudge against Serena, often referring to her as her dad's trophy girlfriend, and resolved to do many things to make sure that her and her dad, Steven would break up. Serena attempted to talk to her in the beginning, convincing herself that she could tame the wild rebel that Sage was, but failed on several occasions. She gets a space for Sage to model in Blair's fashion show, but Sage lets her dress fall, damaging Waldorf Designs image and Blair and Serena's struggling relationship.
Eventually, Sage finds out that her dad is shortly going to propose to Serena, so she goes to Blair for help, and they reach a deal that Blair will stall the engagement by calling Lily and expressing concern if Sage wears a Waldorf Designs dress to Cotillion that night. Sage makes it look as though Steven returned the engagement ring, and sends a message from his phone telling Serena not to come to the Cotillion that night. At the ball, Sage overhears Georgina blackmailing Dan with the sex tape Serena made of them and she steals Georgina's phone to get it. During her presentation statement, the tape streams on the TVs, embarrassing Serena, Dan, and angering Blair. As a result, Steven breaks up with Serena and Nate breaks up with Sage after finding out she was behind the whole thing.
Later on in the Season, Serena runs into Sage and Steven at the grocery store, and invites them to her and Dan's Thanksgiving dinner, because they didn't go to Amsterdam due to Sage not finishing her college applications. At the dinner, Sage makes up with Nate. After being blackmailed by Bart Bass, Nate gets arrested, and Sage goes to visit him, taking his dad along with her to help him get out of prison. While trying to take down Bart, Blair gets together a group consisting of Georgina, Serena, Ivy Dickens and Sage. At New York Real Estate's Man of the Year party, where Bart is being honored, Sage steals the now deceased Bruce Caplin's phone to repeatedly call Bart until he answers. However, Bart purposely drops his phone into a bowl of water after several calls.
Later, Nate is down because he feels as though his life is over due to his arrest and not having a good story to secure The Spectator's future with. Sage says he once had the perfect story, and if they can retrace his steps and find the identity of Gossip Girl, he'll have one again. .
In the series finale, Nate and Sage are trying to find out who Gossip Girl truly is. When they meet with everyone later to make hasty plans for Blair and Chuck's wedding, Dan gives Nate the final chapter of Inside Out which contains the identity of Gossip Girl, and Nate sends Sage to the office to type it all up. That marks Sage's last appearance.
Sage has a very manipulative personality, and is much like Serena was at her age, being the Queen at Constance. Sage can get what she wants, such as breaking up her fathers' relationship with Serena, but she will also care for you if you have grown close to her, such as her relationship with Nate. Sage is not only manipulative, but intelligent and quick thinking. She always knows what she has to do.