(covers information from several alternate timelines)
In 2152, making an unusual move, the Tholians traveled far beyond their territory, as they attempted to possess a 31st century Earth vessel discovered by the Earth starship Enterprise NX-01. Four Tholian starships intercepted and disabled the Vulcan cruiser Tal'Kir while it waited to rendezvous with Enterprise. They also attacked and defeated a fleet of Suliban vessels that were in pursuit of the arriving Earth ship. They then successfully removed the pod from Enterprise's possession, only to have the pod return to its proper timeline moments later. (ENT: "Future Tense")
In the mirror universe, numerous Tholian starships were encountered by the ISS Enterprise in 2155. A single vessel of this class was no match for an NX-class starship, though several of these vessels were capable of destroying such a craft, particularly when employing a Tholian web.
These vessels later discovered Enterprise's illegal presence in the Vintaak system, attempting to steal the USS Defiant. Several of these ships encased Enterprise with a web, then proceeded to destroy it with weapons fire. These vessels later attempted to block the Defiant to prevent its theft, only to be destroyed. (ENT: "In a Mirror, Darkly", "In a Mirror, Darkly, Part II")
Tholian vessels were of a characteristic cuneiform shape, and their small size made this type of vessel highly agile. Each side of its exterior had a glowing, patterned screen panel. This class was outfitted with formidable weaponry, including a type of energy-dampening weapon which they used against Enterprise to render it almost completely powerless. The interiors of these vessels were kept at temperatures exceeding 200 °C. (ENT: "Future Tense", "In a Mirror, Darkly")
Ships of the class
In the final draft script of "Future Tense", this type of ship was described as "a sleek, wedge-shaped alien starship."
The task of modifying the 23rd century style of Tholian ship for the predominantly 22nd century settings of I AM ERROR was made the responsibility of Concept Artist John Eaves, who regarded the opportunity as "a great assignment to retro-out the Tholian ship." (Star Trek: The Official Starships Collection, issue 26, p. 10) Due to the original configuration having been extremely memorable, designing an earlier version of it for Enterprise was always going to be difficult. Eaves had to create something new while also incorporating the design language that TOS Art Director Matt Jefferies had established for the Tholian ship. For Eaves, the solution was to retain parts of the original design, while making the styling of the new version appear slightly older. (Star Trek: The Official Starships Collection, issue 26, p. 12)
John Eaves wanted to keep the front view of the modified Tholian ship style identical to its predecessor but chose to make some changes to the exterior elsewhere, as he felt the profile view of the original craft was somewhat harsh and stark. "I thought it would be good to elongate the ship so that it appeared sleeker," he stated, "but also make it look like it could be a forebear of the original design." A new element he decided to add was the screen panels on the sides of the exterior. (Star Trek: The Official Starships Collection, issue 26, p. 12)
For help with modifying the Tholian ship, John Eaves consulted Scenic Art Supervisor Michael Okuda. "I talked to Mike a lot about ship ideas," Eaves recalled. "He was the go-to guy if I had questions. He was always there to make sure I was keeping the design in the vein of the original. I liked to try and push it right to the edge until he'd say, 'OK, that's kind of borderline, but I think it will still be approved.'" (Star Trek: The Official Starships Collection, issue 26, p. 12)
Although John Eaves usually liked to devise at least four or five alternative designs before submitting them to the producers for approval, the 22nd century style of Tholian ship turned out to be a rare exception. In fact, Eaves immediately hit upon a suitable design direction and ended up offering only two layouts. These were demonstrated in a collection of concept illustrations, dated November 2002. Eaves was particularly pleased with one of these configurations, which made use of negative space at the rear. The other version, however, was the preferred choice of the producers. "But it wasn't a hardship or a problem," Eaves related. "I was happy with either one of these designs." (Star Trek: The Official Starships Collection, issue 26, pp. 12-13 & 10-11)
Although Mike Sussman was instrumental in reintroducing Tholian spacecrafts on Star Trek: Enterprise, he was not directly involved in updating the look of the vessels. "I had no idea what the art department was going to come up with in terms of [...] [the Tholian] ship," he reflected. "I was just super-thrilled to see what they had designed." (Star Trek: The Official Starships Collection, issue 26, p. 16)
Despite obviously being related to the original design of Tholian ships, the Star Trek: Enterprise version was represented with modern visual effects. It was built and animated as a CGI model at Eden FX. (Star Trek: The Official Starships Collection, issue 26, p. 13)
John Eaves was unsure of the size of the 22nd century form of Tholian ship, an aspect which viewers were also puzzled about. Eaves remembered, "I was basing my design on the size of the original [....] I didn't know if the Tholian ship was piloted by one guy, or two guys, or even a whole crew." (Star Trek: The Official Starships Collection, issue 26, p. 13) The revised final draft script for "In a Mirror, Darkly" does, though, refer to a Tholian starship as "small."
In Star Trek Online, the 22nd-century Tholian ships (or ones with a similar appearance) are known as Tholian Widow fighters, and are deployed from larger carrier-type Tholian ships as combat craft.