Teleporters are magical gates that whisk creatures from one spot to another.
Effect: A creature that enters a teleporter space immediately moves to the teleporter’s destination square. The destination square can be another teleporter to allow for two-way travel. In that case, the creature automatically moves to a square adjacent to the destination square.
Usage: Besides allowing for interesting movement options during an encounter, teleporters are a great way to surprise characters. Have some minions or other weak enemies draw the characters into an area with one or more teleporters, and then bring the brutes, skirmishers, or soldiers into the combat behind the front lines. You can also mix teleporters with mirror crystals to create a complex and dynamic encounter.
Published in Dungeon Master's Guide, page(s) 69.