Homeworld
Little is known of the Vorlon home-world other than its name, which is also Vorlon. Vorlon territory was restricted to other alien species and every known expedition into Vorlon space failed to return to their respective governments. Much like their First One brethren The Shadows, Vorlon is protected by an array of highly advanced and automated defense systems designed to keep out intruders and primitive spacefaring races. These defense systems remain in place and active even after the Vorlons abandoned their home and left known space; evidence suggests that the systems will not allow outsiders entry to Vorlon until 1,000,000 human years has elapsed.
It is suspected that the Vorlon atmosphere is a highly toxic combination of noxious gases which are harmful to almost all known species. During his time serving as ambassador to Babylon 5, Kosh's quarters were flooded with these gases, but Kosh himself was able to wander the station without additional atmospheric support. This, in addition to the incorporeal nature of their species, has led to speculation that Vorlons do not actually require an atmosphere, and instead utilize it as a deterrent to discourage visitors. When human telepath Lyta Alexander journeyed to Vorlon space to contact them, she was physiologically altered to breathe the atmosphere and serve as attache for the Vorlon embassy.
Aside from Alexander, only one other human has been known to have access to Vorlon space: Sebastian, formerly known as Jack the Ripper, whom the Vorlons took from 19th century Earth in order to employ as an "Inquisitor". His fate after the Vorlons left is unknown, though Sebastian hoped that after centuries of "penance and service" he would finally be allowed to die.
Read more about this topic: Vorlon