Extremely xenophobic energy beings of superior technology, capable of manipulating energy fields on many levels and also able to penetrate the U.S.S. Enterprise NCC-1701-D shields even when the shield form and frequencies are varied.  They can also and inhabit another life form, without danger to it, for communication purposes.

Their "wormhole" stun-trap keeps away most visitors or robs their memory of the Paxans, but Lieutenant Commander Data's positronic brain is unknown to them and they threaten destruction of the Enterprise — twice — until Captain Picard convinces them that their memories can be erased and Data agrees to share the event with no one.