When Guthix created the world, it is believed he also created a gateway through which the many worlds, or universes, could commune, though specifically designed to link Gielinor's realm with another dimensional plane, that of the humans. Its only known users are the humans, who arrived in Gielinor during the First Age. The gate is thought to have been sealed soon after their arrival, but whether by Guthix or some other deity is unknown.
Since then, none have been able to access Gielinor directly through the portal. Instead, beings from other worlds have found alternative methods of entering, usually through unstable portals, fairy rings or other means of teleportation.
Whether or not the Portal of Life will ever be opened again is unknown. If it ever were to be opened, this would open up countless possibilities for Gielinor. The potential dangers of connecting Gielinor to other worlds may have caused the gate to be sealed by Guthix.
According to the Co-ordinator, the Fairy Queen harnessed the magic of a powerful portal that had been sealed for centuries to create the fairy rings, though not as powerful as the portal would have been.
It is possible that the portal that the humans came from leads to our world, and they came from Earth. Guthix also refers to a planet named "terra" orbiting a star called "sol", though the planets inhabitants call it "earth" and the star "sun", which is a reference to our own planet and sun.