What you need:
TTF2Font: download it from Sourceforge.net
A font file.
After you have extracted ttf2font, you can create a 'default.cfg' and a 'default.png' by simply passing the font file to the program (either in the console/command prompt or by dragging and dropping the font on the executable). Both files will appear in the current working directory. Open 'default.cfg', the third line should look somewhat like this:
font default "default.png" 35 66
If, for example, your font is called 'revolution', change that line to:
font revolution "revolution.png" 1 35 66
Save the file. Now rename those two files to your font's name, eg 'revolution.cfg' and 'revolution.png'.
All you have to do now is copy the files to "/ReveladeRevolution/data/fonts/", the game should automatically detect the new font. When you're in-game click options->gui and it should be listed with the other fonts, click it to set it as the default font.
TTF2Font is a utility program designed to create font bitmaps for Cube Engine
games, it works by taking a Truetype font and building it into a set of
coordinates in an image. It was created by Quinton "quin" Reeves and
Lee "eihrul" Salzman, to assist Joshua L. "verbalshadow" Blocher in his
creation of content for Blood Frontier.
For more information read the 'readme.txt' that comes with the program.