What this mod changes are it's in-game animated portrait, and win and lose portrait. It lets you play as the 'evil' Eris from the main story mode. Also the file is a .zip.
I did not make this mod I have found it on the internet, and I would like to give credit to it's creator but it was under Anonymous so I can't really give credit unfortunately. This is the link where I have obtained this mod from.
Shade Eris Mod V1: https://mega.nz/#!oJIXAAYS!q3yZRm8SQ6-fMSCfhXG8t7dE91VM69WEnwNsvELw0hI