Teleport control is a property that complements teleportitis. Whenever you teleport (whether from teleportitis, wand, scroll, trap, quantum mechanic attack, or throne effect), you can choose the destination of your teleport, regardless of whether it is an intralevel teleport or levelport.
If you are stunned you will be unable to control your levelports. If you are confused your levelports may take you to a random level instead of the one you pick ("Oops..."); this chance is dependent on your luck (rnl(5)). 
If you select a region of the screen you cannot occupy (inside stone), or a square with a trap or boulder or already occupied by a monster, you will instead be sent to a random point in the level with the message "Oops . . . ."
If you try to levelport to too deep a level--if you say "99", e.g.--you will be sent to the lowest possible level from your current position, which generally means the bottom of your current dungeon branch. A controlled levelport from anywhere in the Dungeons of Doom cannot take you deeper than the Valley of the Dead; a controlled levelport from anywhere in Gehennom can take you only as deep as the vibrating square level until you perform the invocation ritual.
Teleport control also allows you to attempt to teleport to escape drowning if you have teleportitis or are a teleporting monster.
Teleport control can be acquired extrinsically by wearing a ring of teleport control or carrying the Master Key of Thievery, and intrinsically by achieving experience level 17 as a wizard or monk, or possibly by eating a tengu or the Wizard of Yendor.
- "You feel controlled!"
- You gained teleport control through level gain
- "You feel uncontrolled!"
- You lost teleport control through level drain
- "You feel in control of yourself."
- You gained teleport control through eating a corpse
- "You feel centered in your personal space."
- You gained teleport control through eating a corpse, while hallucinating