Cythera uses the font "Argos A Nouveau" for almost all the text in the game. This is a common font that is freely available in high quality today from many font distributors. The more interesting font in the game is the "Seldane" font. This is used for many of the Seldane objects, like pylons that may be opened by the Crolna. While no one has quite decyphered their language, the font is a fun little aspect of Cythera that is unique to the game. The character mappings are shown below, as extractd from ResEdit.
The Seldane font is available in three forms. The first two forms ("Seldane Medium" and "Seldane Large") are bitmap fonts extracted directly from Cythera's game data. The third font ("Seldane.ttf") is a TrueType font based off of the bitmap ones. The TrueType font has superior quality as well as better compatibilty with most font viewers.
(Right-click and choose to download the linked files)
Cythera's images, audio, and text are owned by Ambrosia Software Inc.