Portals
Following the Sundering, the dragons ruthlessly attempted to close any permanent link between this world and another seeing them, reasonable, as potential invasion routes. Stone circles, holy windows, gates to hell, all were forcible sealed often destroying them in the process. Though there were so many that some, inevitably, escaped, a few were hidden before the dragons could chase them down, and some that require specific alignments of circumstance to open were either missed or ignored. Some of the more ambitious dragons hid gates with the intention of using them to their advantage, not all survived to do so.
