From Quake Wiki
Description: A trigger used to teleport players and monsters. Is activated when walked on unless it has a "targetname", if a "targetname" is present the teleporter will teleport once the targetname is called by another trigger.
|angle||The angle in which the teleported monster/player will face when it "comes out" of the teleport.|
|target||Teleport destination name to teleport to.|
|targetname||Trigger name (optional) - only teleports once activated if targetname is present.|
Teleporting Monsters: You can precisely teleport monsters into new locations in Quake. To do so, you must first create a out of reach area for the monsters to reside in. Give this area a trigger_teleport tag and assign a targetname tag to it. Create a teleport_destination where you want the monster to appear. Now, you must create a trigger whose target property points to the trigger_teleport's targetname. When this trigger is activated, the monster in the room will teleport to the teleport_destination. Make sure that there is only one monster per room and one room per teleport_destination. Otherwise, when the teleport is triggered, all the monsters will telefrag each other (like what happens in E1M7 when you win).