Here is the most recent version (v3) of the Mystic class from Unearthed Arcana.
One of the Nomadic Step discipline's psionic effects is Nomad's Gate:
Nomad’s Gate (7 psi; conc., 1 hr.). As an action, you create a 5-foot cube of dim, gray light within 5 feet of you. You create an identical cube at any point of your choice within 1 mile that you have viewed within the past 24 hours. Until your concentration ends, anyone entering one of the cubes immediately teleports to the other one, appearing in an unoccupied space next to it. The teleportation fails if there is no space for the creature to appear in.
Does this mean I can create the second cube a mile up in the sky, and the first on on top of an enemy, or as a readied action - in response to an enemy approaching me, to effectively drop them from 5000 ft up in the sky (taking them out of the fight for a minute and dealing 20d6 damage from the fall)?