A Gorn starship was a type of vessel utilized by the Gorn Hegemony during the mid-23rd century for conducting raids. The Gorn ship was designed with four nacelles, and its class configuration was unfamiliar to the Federation prior to the late 2260s.
In 2267, a Gorn starship approached the Earth outpost on Cestus III at space-normal speed using the outpost's regular approach route. Before the outpost knew what hit them, the Gorn ship knocked out the outpost's phaser batteries with their first salvo, leaving the outpost defenseless. The weapon used was described by a survivor as being "like phasers, only worse." The Gorn ship continued to assault the outpost, until it was obliterated, killing a vast majority of the crew and their families.
The Gorn starship later attacked the USS Enterprise, which had been lured to the colony by false signals. The Enterprise's counterattack with full phaser and photon torpedo banks proved ineffective against the deflector screen of the Gorn ship, which was located just outside visual range.
After the Gorn ship retrieved its landing party via transporter, it withdrew from Cestus III, and attempted to flee into an area uncharted by the Federation at that time. The Enterprise pursued, and eventually overtook the Gorn ship at Warp 8, before both ships were immobilized by the Metrons. (TOS: "Arena")
The Gorn ship did not appear in the original version of the episode, but rather, was conceived for the remastered episode that aired in 2006. StarTrek.com cites the reason for this to be partially because the producers were given "a certain amount of leeway, given time and budget considerations, to be a bit creative." The site describes a design that "reinforces the concept that to achieve warp speed capabilities, nacelle-type structures are required and that a dorsal command center/bridge is also standard." Visual Effects Producer Michael Okuda was the one who usually designed the new ships for the remastered series, but in this instance gave Visual Effects Supervisor Niel Wray the opportunity to do the honors. "I thought 'how cool, I can design something totally new for Star Trek.", Wray gleefully commented.  The ship was only shown at a distance, both the viewscreen and in space afar from the Enterprise "to stay consistent with the original story intent." The CGI model of this ship itself was therefore not "skinned" (thereby saving costly computer rendering time) because the ship was never shown up close.  The new, digital model was constructed at CBS Digital in the Autodesk Maya CGI software. (Sci-fi & fantasy modeller, Vol. 26, p. 49)
In 2015, former Star Trek Producer Dave Rossi made the entire starship database of the remastered Original Series available to Project Manager Ben Robinson for representation in the British partwork publication Star Trek: The Official Starships Collection from Eaglemoss Collections.  However, these models, including the Gorn starship, were not quite production and/or print ready as the models needed to be converted into LightWave 3D, the software package of choice for the vast majority of Star Trek digital modelers. Robinson assigned Fabio Passaro, among others, to this chore. 
In 2016, ten years after the airing of the remastered episode, a model of the Gorn starship was announced as part of The Official Starships Collection. It was given coloration and final details by Michael Okuda. This improved CGI model was featured in the Star Trek Encyclopedia (4th ed., vol. 1, p. 310).
- Star Trek: The Official Starships Collection, issue 86, 2016