The Guardian of Forever, the time portal portrayed in the episode, is an irregular ring- or torus-shaped structure perhaps twice the height of a human. It illuminates brightly from within with each spoken word or phrase. It has a rough, weather-beaten appearance, implying extreme old age, as if it were a geological formation such as a natural arch. It is situated amid Classical stone ruinsionic columns are recognizableas if it were once the focus of a now abandoned temple. The central aperture, through which characters enter or return from past times, also serves as a kind of viewing screen through which distant epochs may be observed remotely. The Guardian presents and plays past events chronologically as in a motion picture and a traveler may thus select a point in the past to visit.In the Star Trek universe, analysis of the ruins on the Guardian's home world suggests it may be billions of years old but no one knows who built the Guardian. The Guardian is able to speak to anyone who asks it a question, though the meaning of its responsesin oracular fashionis not always clear. For instance, when asked if it was machine or being, it responded, Both ... and neither . When Spock says I see no reason for your answers to be couched in riddles , the Guardian states I answer as simply as your level of understanding makes possible , and continues that the character's science knowledge is obviously primitive . The Guardian of Forever the entity's own name for itselfspeaks rather bombastically in a mellifluous male human voice. It can detect changes in the timeline, but typically provides its users little help in figuring out how to change it back. Being near the Guardian when such changes occur isolates those from the effects of the change in the timeline. Since its original appearance, the Guardian of Forever has been featured in many spin-offs, tributes and parodies. Show less «