Entity

An Entity in this usage means a creature that is incorporeal, but can have an effect on a character or the environment.
Entities can have different motives drives and goals. There seem to be numerous different types, an entire insubstantial menagerie. Many can bond with people or possess people. Some can possess items such as computers. Some can alter their environment using mysterious means or by creating illusions. Some are friendly, some are hostile. Some just want to escape and at least one was just bored. A disappointing number seem to eat something about people. Many are Sentient, but some aren't. 
Several such creatures appear in Star Trek - Examples below are from TOS, TAS and TNG. I am sure DS9, VOY and ENT have their fair share as well.
==Examples==
TOS season 2 - Metamorphosis - "Companion"
TOS season 2 - Wolf in the fold - "Redjac"
TOS season 2 - And the Children Shall Lead - "Gorgan"
TOS season 3 - Day of the Dove - Unnamed entity
TOS season 3- The Lights of Zetar - Zetarans
TAS season 1 - beyond the Farthest Star - Magnetic Entity
TAS season 2 - The Practical Joker - Practical Joker 
TNG season 1 - Lonely Among us - Unknown name - blue energy
TNG season 1 - Skin of Evil - Armus (Arguably)
TNG season 2 - The Child - "Ian Andrew Troi"
TNG season 3 - The Bonding - Koinonian Individual(?)
TNG season 5 - Power Play - Ux-Mal Prisoners
TNG season 5 - Imaginary Friend - "Isabelle"
TNG season 6 - Timescape - Aliens take the forms of Romulans
TNG season 7 - Interface - Subspace Alien appears as Geordi's Mom
TNG season 7 - Phantasms - Invisible and unfelt creatures, Interphasic parasites are eating the crew and giving Data nightmares
TNG season 7 - Sub Rosa - Ronin, the Anaphasic life form, wants to eat Beverly's brain.
==Meta==
For story telling purposes these entities function approximately the same way as ghosts and spirits do.
In all of these the Star Trek rules apply - the bad guy isn't a bad guy in his own mind. The key is understanding where he comes from.
Once understood, the creature goes from spooky menace to either a challenge to be met, or a conflict to be resolved. Understanding is power. These creatures are scariest when the characters and we don't understand them clearly.
Once they understood what they were dealing with, the Enterprise-Prime crew was able to turn the tables on Redjac. The Companion acted from love, which the crew encouraged. Picard explained humanity some to the Imaginary friend "Isabell" and out maneuvered the UX-Mall Prisoners in "Power Play."
Properly handled, an Entity can make for a good story. Poorly handled, you get "And the Children Shall Lead..." - a result which speaks for itself.
The excuses for such creatures vary from magnetic patterns and pure energy to Anaphasic and Interphasic creatures.
==Epiphnay Trek==
I do not assume a single source or cause for Entities. As biological life can take many forms, so can non-biological life. Per Example RIs have been described as an incorporeal life form with the restriction of "must live in a computer". The reason being they can switch bodies. Something the average biological cannot.
In Jay's terms there is no single special effect. 
==ST:OM==
I haven't decided what Special Effect such creatures work on for ST:OM. However, my intention is to dream up a reasonably consistent idea and stick to it. Like Time Travel or any other form of techno-magic I feel that getting my story straight and sticking to it makes it better.
Jayphailey 02:55, December 29, 2009 (UTC)
Category:Lexicon
Category:ST-OM
Category:Epiphany Trek