After jumping into the tangle of red roots deep within the Hornet Hive, Commander Keen finds himself once again under the crystalline mountains. Before him is a towering stone temple, built by the Krile many centuries ago, the Crystal Sanctuary. Ancient and foreboding, this temple is where Cyraaun Kriuus Llquo and other Krile have taken refuge from the Atroxian Realm spreading across their planet. In order to reach them, Commander Keen will need to solve the puzzles and brave the dangers within the sanctuary, eventually reaching the top where he can find a quick way into the chamber where the Krile are hiding. The Atroxians do not know of this place, and thus are not seen here. Krisle's native species will not set foot in the temple itself, though a few lonely Spliders roam the outer areas of the cave in which it's built.
Of interesting note are the many rainbow-colored question marks scattered about the Crystal Santuary. When collected, a randomized item will be added to Keens score, which will either be a Spark, a Spark Star (Extra Keen), or a random point item (100, 200, 500, 1000, 2000, or 5000 points).
- Atroxian Realm - Page on this Wiki