The End of Days mod adds a new playable faction to the game – Russia, as well as improving the original three factions with new units, structures, and special powers. The aim of the mod is to enhance the gameplay experience and provide players with new strategies and challenges. With the addition of Russia, players can now command a completely new set of units and structures, which opens up new tactical options on the battlefield. The mod is designed to be compatible with the latest version of the game, ensuring that players can enjoy the new features without any technical issues. Overall, the End of Days mod is a great addition to the game for those looking for new and exciting content to play.