I have to admit that I am not sure of where the character comes from, so there is no general information available.
Contrary to common practice, there are three graphic files in the directory. However, one seems to be data that have been used in creating the other two files, and the other two files seem to be alternatives for each other based on user preference. As far as I know, Only the one named "Rydia_parasite.png" is actually used by the game.
This area could be used for special comments about the character.
For more detailed information, see the commented version of Rydia_parasite_ed.txt.