The Portal was a Tenctonese relic that held religious significance amongst the species as it was used to provide users enlightenment. It functioned by generating an energy field that created a virtual world around a group of users with its effects being similar to hallucinogenics. An individual's subconscious mind, however, made the experience slightly different from their comrades. This allowed them to witness remarkable new vistas and lost loved ones thus giving a user renewed hope. Typically, it was used selectively by venerable Elders of Tenctonese society who held a monopoly on the device and used it to for their own personal journeys.
When properly used, the Portal provided a glorious mind expanding experience though seekers needed to be carefully schooled first as there were dangerous elements involved in using the device. Those seeking a quick path towards enlightenment by improper handling of the device faced great danger. This was due to the subconscious impact on the Portal's effects that allowed each user to bring their own angels or demons to their experience. Thus, fear and desire were considered dangerous elements that impacted a user's journey in the Portal. This was why guidance in its usage was essential as the mental stability of each user was critical.
This relic arrived on the planet Earth when the Tenctonese crashed on that world. This artifact was kept contained in a Tenctonese shrine and cared for the by elders tending to the site. However, a fire was started at the site and it was believed the Portal was lost. In reality, the device was actually stolen and used by an underground cult who began offering it to select disciples. These improperly trained imbalanced individuals began returning into society where they attempted to kill their demons thus creating societal disruption as well as attracting the attention of the police. (Alien Nation: Millennium)