Here's why:
* Knuckles' Story: Knuckles' storyline takes place primarily in the Angel Island levels, not Mystic Ruins. His goal is to protect the Master Emerald, leading him to confront Eggman on the island.
* Eggman's Role: Eggman's main focus in the game is collecting Chaos Emeralds. While he appears in various levels, his primary encounters are in stages like Emerald Coast, Windy Valley, and Final Egg.
However, you can find Knuckles and Eggman in Mystic Ruins through the Adventure Field mode, which allows you to explore levels freely after completing the main story.
Here's where to find them:
* Knuckles: He's usually located near the entrance to the Mystic Ruins level, offering challenges and hints about the Chaos Emeralds.
* Eggman: Eggman might be found in certain areas of Mystic Ruins, especially if you trigger specific events or complete certain tasks within the Adventure Field.
Remember that these locations can change depending on your progress in the Adventure Field and the completion of certain events.