Architects

Little-known alien race responsible for creating door-sized "gateways," devices capable of sending the user across space and time without seeming effort, or even to parallel universes. One such device somehow found its way into the back wall of the Good Time Chinese Restaurant in Lawndale, which led to the bizarre adventures recounted in the third-season episode "Depth Takes a Holiday." The Architects were first mentioned in "Illusions" and resurfaced in "Guys' Night Out."

In "Illusions," the supernatural character Angel said the Architects were "aliens from another arm in this galaxy. The Architects made those inter-universal gateways about half a billion years ago, loads of them, and ran all over the place with them. Beings that find the gates now tend to hide them away for whatever purpose they can dream up, like sneaking into other people’s homes—or invading other worlds or universes." She added that the Architects "are all gone, dead most likely."

Angel noted that each gateway emits a "a multi-planar resonance signature," a kind of telepathic nudge that acts as "a come-hither signal, a way of ensuring that someone finds it." Such signals manifest themselves in various ways (dreams, ideas for stories, visions, etc.) but are very similar, directing the recipients to a specific location (such as the Good Time Chinese Restaurant) so the gateway can be discovered and utilized. However, unknown to everyone, the gateways are also intelligent and possibly malign, often sending the users to dangerous worlds or disastrous encounters, perverting the intent of the user. Use of a gateway also appears to be psychologically addictive, causing travelers to never stop using them until the travelers are destroyed by what they encounter. Angel herself is vulnerable in an undefined way to the presence of the Architects' gateways. Were she to use one, it might induce a sort of insane power hunger in her that she described as similar to what Galadriel (of The Lord of the Rings) claimed would happen to her were she to receive the One Ring.

Gateways were the last devices created by the Architects, who became entirely extinct within an extremely short time after the gateways were employed. How that happened, or why, is unknown, but the gateways may have deliberately brought that end about.