Master Sergeant in the U.S. Marine Corps, assigned to Icarus Base before escaping an attack through the Stargate and onto the Ancient exploratory vessel Destiny -- millions of light years away from home.
Greer had a difficult relationship with his father, a war veteran who pushed Ron hard and had difficulty showing affection. As a young man his father evidently set their house on fire in a suicide attempt, and when Ron returned home he rescued his father and sleeping mother from the flames. But he didn't let his father's disturbed condition change him, instead enlisting in military service to follow in his footsteps -- a testament to Ron's character.
Greer's own military record is far from spotless, however. Before the attack on the Icarus Base he was in the brig, facing charges from assaulting a senior officer, Colonel Telford. Colonel Everett Young released him from the detention wing and advised him to take his anger out on the base's attackers. Now aboard Destiny, he is effectively out of reach of the military judicial system. Despite Greer's altercation with Telford, Colonel Young fervently believes in the young soldier's integrity.
Despite his volatility, Lt. Matthew Scott places a great degree of trust in him and Greer has proved himself to be a capable soldier.
Air, Part 1 - Colonel Young drops pending charges against Sergeant Ronald Greer in exchange for helping the Icarus personnel evacuate through the Stargate.
Air, Part 2 - Greer allows Senator Armstrong to sacrifice his life and seal a hatch that was leaking the Destiny's already limited air supply.
Air, Part 3 - Greer risks his life to forage into the desert of an alien world to ensure Lieutenant Scott makes it back to the Stargate in time.
Light - It is revealed that an assault on Colonel Telford is the reason Greer was in confinement pending charges.
Justice - After taking command of the ship, Camille Wray removes Greer from the off-world duty roster.
Lost - Left behind on a planet after Lt. Scott believed Ron was killed in a cave-in, he recalls his rocky relationship with his war vet father.
Pain - Infected with an alien tick, Greer is convinced that Wray and Rush are plotting another attempt to take over Destiny, and hunts them down and nearly kills Wray to stop them.
Alliances - Greer reluctantly uses the communication stones to visit Earth, only to be trapped inside a Homeworld Command facility with Camille after a Lucian Alliance attack.
Hope - With Dale Volker's life on the line Greer selflessly offers to donate a kidney in a risky surgery.
The Hunt - Searching the woods for two of the crew who have been taken by an alien creature, MSgt. Greer struggles with his failing self-confidence after failing to take a key shot.