Mirror Menace, also known as Keen 10 is the first episode of the Dimensional Chaos trilogy that follows Keen 9: Battle of the Brains. It’s the first Keen 6 mod made by Szemigi . The story continues where Battle of the Brains left off. After saving the universe from Mortimer McMire Keen made his way back to home with his friends. They were flying when Lt. Barker told Keen a blue vortex is coming behind them. Unfortunately, it sucked them in and after a short landing they founded themselves on a planet that’s similar to Shikadus I.
From http://www.shikadi.net/keenwiki/Keen_10:_Mirror_Menace