A Keldra Gateway was an advanced magical action used as a method of teleportation. A Keldra Gateway was more commonly known as a dreadgate. Its last known usage was by the Draol Atury during the Great Purge; the action was beyond Atury's power and he, along with his minions and a portion of the armies who hunted him, were erroneously transported to the world of Errod. Unknown to all but a handful, Atury's mentor Orilac also utilized a dreadgate in an attempt to escape the Purge; he and his followers were never seen or heard from again.
Utilization
Using a dreadgate was considered a very advanced technique, and it functioned like a reverse summoning; one essentially "summons" themselves someplace else. Where Atury went wrong was in thinking it functioned similar to perciperation, where transports through time or space in the Dream Lay in order to access deep memories by focusing on the target and honing in on it.