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Because I am not Starfleet. We are far more resourceful. That's how we found you. And don't worry...we know how to keep a secret.
We do what we do so you can do what you do.
~ Leland to Christopher Pike.
Leland is an antagonist introduced in a bonus scene from the Star Trek: Discovery episode "Will You Take My Hand".
He was portrayed by Alan Van Sprang.
Earlier in his career Leland was friends with Christopher Pike. The two would later have a bit of a falling out over Leland's involvement with Section 31.
Leland was a member of the unsanctioned United Federation of Planets agency Section 31. Shortly after the end of the Federation-Klingon War of 2256-57 he disguised himself as a Trill and travelled to the Klingon home world of Qo'noS. There he located the mirror universe version of Philippa Georgiou, who was running a bar in the Orion embassy on Qo'noS.
Once there he approached the mirror Georgiou and made her an offer to join Section 31, explaining that even though there was a cease fire in place the galaxy was still a dangerous place, and that Georgiou could still influence the galaxy. When Georgiou mentioned that Leland did not sound like Starfleet, Leland said that he was not Starfleet, but a member of a much less restrictive agency.
Giving her a black Starfleet delta, Leland welcomed her to Section 31.
Control informed Leland that it considered Ash Tyler a prime recruit for the agency. Leland passed that information on to Georgiou, telling her that she needed to work on her recruiting speech.
After Control's true intentions to become sentient and wipe out all other sentient life in the galaxy were discovered the AI incapacitated Leland, and then downloaded itself into Leland's mind, destroying his original personality in the process. Control used Leland's body in an attempt to gain data on artifical intelligence that Discovery had received from an ancient sphere before Discovery's crew could send the data to a time where it could not retrieve the data.
Control escaped from Essof IV, and Discovery was unable to pursue the AI as Control had masked the ship's warp signature. Taking over of the rest of Section 31's fleet, Control took the fleet to Xahea to capture Discovery before it could be taken into the future and out of Control's grasp.