(covers information from several alternate timelines)
The Gorn captain was an officer in the military of the Gorn Hegemony in 2267. He commanded a Gorn starship comparable to the Starfleet's Constitution-class vessels, as well as a detachment of ground assault forces. The captain made first contact with Humans in forced personal combat with James T. Kirk.
Assault on Cestus III
The Federation's establishment of an outpost colony on Cestus III, was regarded as an invasion of Gorn territory by the Hegemony, and the Gorn captain was tasked to respond to the threat. Approaching at space-normal speed in the manner of a friendly vessel, the captain opened fire at close range, destroying Cestus III's phaser batteries. Defenseless, the outpost offered to surrender, but the plea went unheeded or unheard. The installation was promptly destroyed, resulting in the death of nearly all inhabitants. He remained in the system after the assault, and monitored the approach of the USS Enterprise, the Federation's key military asset in the sector.
The Gorn captain's ability to mimic Starfleet communications fooled his new opponent, Captain James T. Kirk. Expecting a warm welcome from the Cestus III base commander, Commodore Travers, Kirk's landing party beamed into an ambush, surrounded by Gorn ground forces and pelted by disruptor artillery fire. Simultaneously, the Gorn starship quartered-in on the Enterprise while she was locked in orbit. The ships were evenly matched for firepower and deflector screens. Unable to maneuver the Enterprise from her position, Lieutenant Hikaru Sulu was forced to break orbit, temporarily stranding the landing party.
His ingenious counter-strike to the (perceived) Federation invasion was foiled by an inability to secure or destroy the Cestus III armory. Kirk managed to liberate a grenade launcher and pushed Gorn ground forces back, forcing them to retreat to their ship. With his planet-side forces repelled, and the Enterprise now free to maneuver, the Gorn's early advantage evaporated. He set his ship on a course for home at high warp. Enterprise retrieved Kirk from the outpost ruins and began pursuit, intending to destroy the Gorn starship.
Battle with Kirk
The chase brought the vessels through a sector overseen by the Metrons, an advanced and powerful species that abhorred violence and who were unknown to the Federation at the time. Whether the Gorn Hegemony, a stellar neighbor, was aware of the Metrons and their likely response to belligerents in their territory, is unknown. Offended by the incursion, the Metrons disabled both the Gorn starship and the Enterprise.
The Metrons declared the two commanders would face each other in single combat, rather than wreak havoc in a space battle. The surviving Captain and ship would be allowed to depart, and the dead Captain's vessel and crew would be destroyed. In a blink, both captains were transported, disarmed, to the surface of a desert planetoid for their appointed battle – the first known face-to-face contact between Human and Gorn.
After a brief initial grappling that proved the Gorn captain's physical superiority and Kirk's relative agility, the conflict escalated into a battle of wits. As they jockeyed for position around their rocky arena, both captains fashioned traps from available materials that countered their opponent's advantages. In pauses between attacks, the Gorn eavesdropped on Kirk's reflective monologues, via a recording-translating device provided by the Metrons.
Eventually, the Gorn captain tired of tracking the Human's scurrying back-and-forth movements. He implored his prey to give up, and insisted his killing blow would be mercifully quick. At last, the Human lingered in one spot, frantically working on a hollowed log that would make a poor club. The Gorn approached, oblivious to the coming explosion and the diamond projectiles that would embed themselves in his chest.
Kirk moved in to finish the kill, but coming to understand that the Gorn was merely acting in the defense of his territory, he protested the Metrons' arbitrary rules and refused to murder his erstwhile enemy. A Metron recognized Kirk's compassion, and returned both captains alive to their ships. (TOS: "Arena")
The battle of the two captains was well remembered over a century later. When Captain Benjamin Sisko had the opportunity to meet Kirk in a time travel incident that sent the USS Defiant to 2267, he wistfully said, "I'd like to shake his hand and ask him about fighting the Gorn on Cestus III." (DS9: "Trials and Tribble-ations")
The Gorn captain (the "Gorn") was played by Bobby Clark, Gary Combs (both uncredited in the rubber suit), and William Blackburn (who only wore the Gorn head for close-up shots), and voiced by Ted Cassidy. The Gorn's costume was designed by Wah Chang, who also created the M-113 creature (aka the Salt Vampire). It had vent holes to allow the wearer to keep cool. (Star Trek: Lost Scenes)
The Star Trek Customizable Card Game gives his name as S'salk. The RPG book Demand of Honor calls him S'slee. The RPG book Planets of the UFP calls him Rheuzz'r. The comic Directives and Dying of the Light and the novel Seize the Fire call him S'alath. The Star Trek Adventures - Core Rulebook calls him Arijog, but the more recent Star Trek Adventures - Beta Quadrant sourcebook goes back to calling him S'slee.
The game Star Trek: Attack Wing uses images of the Gorn captain to represent the characters S'sesslak and Lahr. It's unclear which of these, if any, is supposed to be the Gorn captain who fought Kirk.
The comic book The Boy, The Warrior, and The Veteran reveals that S'alath contracted a neurodegenerative disease and spent the last years of his life on a planet, fighting holograms of Kirk. Hikaru Sulu and Kang travel to the planet to investigate rumors that Kirk is alive. S'alath attacks them and is killed by Sulu.
The short story Where I Fell Before My Enemy reveals that the Gorn captain helped to negotiate a treaty with the Federation, but later returned to Metron space. In 2373, he approached Benjamin Sisko on behalf of the Metrons. By this time the Metrons were a dying race and they wanted to preserve their knowledge for future generations.
The Star Trek Adventures - Beta Quadrant sourcebook claims that S'slee was executed for his failure shortly after the events of Arena.
- See: Elysia inhabitants
Pregnant female and octuplets
In the alternate reality, while preparing to aid Carol Marcus in disarming an advanced long-range torpedo, Leonard McCoy bragged about once having performed an emergency Caesarean section on a pregnant Gorn, delivering her live octuplet babies. According to McCoy, the infants came out biting. (Star Trek Into Darkness)
The skeletal remains of this unfortunate individual were kept in a display case as part of Captain Gabriel Lorca's "menagerie" on the starship USS Discovery in 2256. (DIS: "Context Is for Kings", et al.)
In 2380, Ensign Samanthan Rutherford of the USS Cerritos crash-landed on a planet where a Gorn wedding was taking place. Among those in attendance were a bride, her groom, a priest, and multiple guests. When Rutherford accidentally called attention to himself, the guests attacked him, and began to physically gnaw at him. (LD: "Veritas")