Actually, there's a few abilities (read: spells and powers) that would be critically helpful with the problem of teleportation. Divert Teleport is the easiest to get at level 13 for Psions, followed by Dimensional Lock at level 15 for Clerics, Wizards, and Sorcerers. To solve the problem of how they can have those effects without having a bunch of high-level casters around, they all died.
To clarify, the devices were created a long time ago by really powerful casters, and would automatically trigger and project the relevant effect around the location in the event of war.