Portals are magic teleportation devices that allow a user to leave one hex and enter another. Normally this would count as Movement and would be disallowed during the night or off Turn.
The only known portals connect to the Magic Kingdom. One of these portals is known to connect to Gobwin Knob and it did survive the Volcano Uncroaking.
There may be limits on who may use Portals. It is implied that Warlords that use a Portal are disbanded.