Captain Walker Keel: Commanding Officer, U.S.S. Horatio. Suspected that Starfleet had been co-opted by a secret alien influence late in 2364. Brought Captains Rixx and Tryla Scott into his cabal, unaware that the latter had already been turned. Keel grew more paranoid and didn’t trust his first officer or his chief medical officer. Arranged for a secret meeting with Rixx and Scott and brought along Captain Picard. After confirming to his best of his abilities that Picard was still himself, he voiced his concerns to his old friend but without firm evidence, Picard wouldn’t go any further. Not long after the Horatio was destroyed, evidence suggested it was sabotage. There were no survivors. 

Appeared in TNG’s “Conspiracy” 

Captain Paul Rice: Captain of the U.S.S. Drake. A classmates of William T. Riker, he was offered command of the Drake after Riker turned it down. Sent to the planet Minos in the Lorenze Cluster when long range probes indicated that all intelligent life on the planet Minos had disappeared. They reported their arrival to Minos, which was their last transmission. The ship and crew was destroyed by the Minosians’ automated weapons demonstrations program. Rice’s image was later used as a lure for the Enterprise’s away team.

Appeared in TNG’s The Arsenal of Freedom

Admiral Gregory Quinn: Starfleet Admiral in the Operational Support Services Division. Used the Enterprise’s layover at Relva VII to conduct a snap investigation, along with Lt. Cmdr. Dexter Remmick (with the Inspector General’s Officer). The investigation and the interviews were a front to make sure the Enterprise crew and her Captain had not been co-opted, believing forces either internal or external were looking to destroy the Federation from within. Quinn offered Picard the promotion to Admiral and the position of Starfleet Academy Commandant hoping to keep him close while also believing he was the best man for the job. Picard declined and Quinn let the matter drop. 

Some time after Relva VII but before the destruction of thestarship Horatio, Dexter Remmick infected Admiral Quinn with a mind controlling parasite. Admiral Quinn became one of many unwitting aides in an alien conspiracy to take over the Federation. 

Quinn was on Earth when the Enterprise returned following the destruction of the Horatio, along with the Admiralty invited Picard to dinner at Starfleet Headquarters, with first a trip to the Enterprise where he misdirected Captain Picard about his previous fears but only drew attention to himself. Quinn attempted to infect Riker with the parasite, attacking him Only the intervention by an armed Dr. Crusher was Quinn subdued. Medical examinations revealed the alien parasite which had attached itself to the base of his skull and taken complete control. When the Remmick-Queen creature was destroyed, his parasite also perished leaving no trace. He was given a clean of health. 

Appeared in TNG’s “Coming of Age” and “Conspiracy”

Rear Admiral Mark Jameson: Starfleet combat veteran, his final command  was the starship Gettysburg. He contracted Iverson’s disease which was incurable, debilitating and fatal. By 2360 he was confined to a wheelchair and he and his wife were living out his final days on Persephone V. In 2364 he made a deal with the natives of Cerberus II, calling in a favour after a successful treaty negotiation, to get his hands on a near-mythical age reversal drug, enough for him and his wife (unbeknownst to her). When he learned of the hostage crisis on Mordan IV and that Karnas was involved (the man he’d betrayed 45 years ago when he’d secured the release of some hostages in exchange for weapons and ended up arming both sides) he took both doses of the drug, determined to meet Karnas on equal footing. The drug worked too well and he began getting younger and stronger. He was free of Iversons but was de-aging rapidly. The effects had not gone unnoticed by the Enterprise crew, which was ferrying him to Mordan IV. He led a botched rescue attempt, before the age reversal made him unsuitable to lead. He and Picard beamed down to negotiate with Karnas, who did not believe the now teenaged-looking Jameson was the same man who’d betrayed him, but the scar was proof enough to see that it was him. Jameson officially died of organ failure in front of Karnas, his death securing the release of the hostages. He was buried on Mordan IV at the request of his wife and with the consent of Karnas.

Mark Jameson appeared in TNG’s “Too Short a Season”

Commander Orfil Quinteros: Base Commander, Starbase 74. Previously on the team that put the Galaxy-class Enterprise together. Worked with the Bynars when they had upgrades for the Wellington and then the Enterprise’s computers in 2364. When the Enterprise appeared to be headed for a magnetic containment field collapse without any way of stopping it, they evacuated the ship, and set it on an automatic course away from the base. The magnetic field regenerated and the Enterprise warped away. Picard and Riker were still aboard the ship. Quinteros organized the recovery efforts but they had no ships capable of catching up to the Enterprise. The situation resolved itself with Picard and Riker piloting the recovered starship back to the base.

Commander Quinteros appeared in TNG’s “11001001″