Portal 63 was a guardian on a planet in the Delphi Ardu star system that was active over 600,000 years ago during the Age of Bastu as time was marked by the Tkon Empire. He was invested with great powers, including the ability to immobilize starships and could appear in various corporeal forms according to the appearance of the beings he encountered. Portal 63 also had some form of telepathy. He remained inactive until 2364 when the crew of the USS Enterprise-D encountered his outpost along with a Ferengi starship. At that time the Portal learned that the Tkon Empire had fallen shortly after the Age of Makto and that he had been inactive all that time.

Both ships were caught in an energy field around the unexplored planet and sent away teams to try to disable the energy field. After the Ferengi attacked the Enterprise away team, the Portal appeared and threatened both teams. He asked "Who will meet the challenge?" After the Ferengi tried to lay blame on the Humans, the Portal became disgusted with the Ferengi's profiteer responses to his questions. When Riker refused to attack the Ferengi, the Portal was impressed and took an interest in Riker's wisdom. Once Riker passed several of the Portal's intellectual "tests," Riker convinced the Portal to free the two vessels in orbit and they departed. After releasing the ships, the Portal returned to his post until he was needed again. (TNG: "The Last Outpost")

"Portal Six-Three", as he called himself, was played by Darryl Henriques.
In Richard Krzemien's original story, Portal 63 was named "Dilo" and was kind of a caretaker of the planet who slept when the Tkon Empire was destroyed. (Creating the Next Generation: The Conception and Creation of a Phenomenon, pp. 39-40)
The revised final draft of the script described him as "A tall, thin, aged (make-up effect) humanoid figure (Portal) in a fine long robe." Before making his "strike" towards Riker with his staff, the script notes described: "as the Figure seems a bit younger, better muscled, the robe shorter and more practical, with a large, lethal appearing scimitar-like weapon in hand," however his age appeared unchanged in the aired episode.
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