Gateway

Gateway was an arcane alteration spell that opened a two-way portal to a location the caster had previously visited.

Effects
This spell only worked on the Prime Material Plane of the caster, and only provided passage to locations at which he or she had been physically present at some previous time. The gateway lasted for a minimum of sixteen minutes; longer for more experienced casters. The portal appeared as an upright disk 10 ft (3 m) in diameter within 10 yd (9.1 m) of the caster. It could not occupy the same space as another object but could be placed against any vertical flat surface. If cast as a free-standing disk, the back side of the portal appeared as a disk of featureless gray.

When successfully cast, the gateway bridged the two locations like a window, allowing creatures on both sides to look through the portal and see the other side, but keeping the environments separate. For example, if one terminus of the portal was under water and the other on dry land, no water poured out one side, and no air bubbled out of the other. While in operation, living creatures could pass freely back and forth along with whatever they wore or carried. Nonliving matter (or creatures) could not pass through unless carried by a living creature.

Distance was a factor in determining the success or failure to cast this spell. Gateway always succeeded when the chosen location was within about 100 mi (160 km), but as the distance increased to 500 mi (800 km) the spell failed about half the time. There was only a one in ten chance of reaching another planet in the same solar system, and even less chance of reaching another solar system. This spell could not form a bridge to any other plane of existence. If the casting failed to reach the chosen destination, then further attempts to the same destination would also fail, indicating that conditions were not conducive for gateway to operate at that location.

Gateway could be terminated prematurely by the caster at will, or by a successful dispel magic cast on it. When the portal collapsed, anything that was not agile enough to avoid it as it shrank out of existence was severed at the surface of the portal, possibly resulting in lost limbs or instant death.

Components
In addition to verbal and somatic components, this spell required a handful of earth from nearby the caster.

History
This spell was found in a book that was known as Elminster's traveling spellbook although the Old Sage was not known to have claimed responsibility for the book or its peculiar habits. Gateway was later published in Volo's Guide to All Things Magical and became generally known to the magical community and was fairly common.