A species known for the Tholian Web.
The Tholians are a crystalline species who are very territorial and who live in a part of space that is too hot for most other life forms. Little is known about their appearance, since they are seen only briefly, and they are known mainly for their strict, precise sense of time and for their defensive attitude toward their borders.
Their ships create a web of energy that can trap other vessels, and the Tholians are known for being quick to take offence at violations of their space. Their society is not well documented, and their cooperation with the Federation has been rare, but they have a reputation for their patience and their ruthlessness in defence of their claims.
They appear in the original series episode The Tholian Web, in which the Enterprise encounters a Tholian ship near the disabled USS Defiant, and Captain Kirk disappears into interphase space. The Tholians begin to spin a web around the Enterprise, while Spock and the crew race to find a way to save Kirk. They return in Enterprise, where they are shown to have a long history of friction with others.