Bgztl is a planet that exists in exactly the same space as Earth, only in another dimension.
Near the end of the 20th century, a youth named Bgztl led a group of his peers, all of whom had the ability to phase through other objects. In her work for L.E.G.I.O.N., Enya Wazzo brought her into contact with the phantoms, who kidnapped children on the planet Dexll. These thieves tried to trick Phase into believing she was one of them, a long-lost relative. Upon further investigation she discovered that these people were taking children in order to appease a demon called Bhargast. The demon had enslaved the phantom people by stealing their youth. Once Bhargast was gone, these people, led by Bgtzl, chose to colonize his "phantom" dimension. Given their inherent abilities, they were perfectly suited for life there. This phantom dimension would eventually be known as Bgtzl.
The Bgztlians could travel to the Earth dimension, but up until the 24th century, when they sent an ambassador to establish relations between the two planets, they were believed to be ghosts or phantoms.
Most Bgztlians required technological assistance to shift into the Earth dimension, travelling in ships or using other devices, but a select few have such control over their abilities that they can travel back and forth without assistance. Lying between Bgztl and Earth is the Buffer Zone, a dimension the Bgztlians shift into when they become intangible and are able to phase through solid objects.