Tholian vessels are wedge-shaped and are capable of traveling across and within interphasic space.
Tholian vessels, when working together, use a unique form of energy weapon to create a Tholian Web. More than one Tholian ship is required to spin this web, a web of energy in space, used to trap an enemy vessel. The more ships spinning the web, the faster the web is completed. After the web is drawn together, it constricts and finally destroys the vessel inside.
One ship snared in the web, a 23rd-Century starship called the U.S.S. Defiant NCC-1764, was not destroyed. Rather, the starship found itself transported to a Mirror reality, circa the 22nd Century, via the web's seemingy "interphasic" properties.
Tholian ships are incredibly maneuverable vessels, and feature an aggressive armament of weapons. The U.S.S. Enterprise, under Captain Kirk's command, encountered two Tholian ships while investigating the Defiant's distress call. The Enterprise NX-01, under the command of Captain Archer, also encountered the Tholian's impressive -- if not mysterious -- design of space vessel.