Lexicon is a rocky, low atmospheric planet in the same system as Narnia and Mata Nui.
Lexicon's terrain is very forbidding, as it has no blue skies, or natural foliage of any kind. Space is clearly visible from the surface.
As the name suggests, Lexicon's inhabitants are very knowledgeable of various idioms and words. They are most likely the most scholarly race, with even the youngest child having a larger vocabulary than Earthly scholars.
In 3012 AD, Lexicon was destroyed by the True Sith Empire, as a demonstration of their power.