The Castle Keys resemble mostly keys for lever-type locks. They have a slightly flattered, green hexagon-shaped bow with what appears to be a half-closed eye in the middle. They also possess a short shaft and two teeth for a head. They are usually found afloat on the ground.
The Castle Keys appear exclusively in Team Chaotix's version of Mystic Mansion where ten of them are hidden in the Stage. The player's objective here is to collect all ten Castle Keys. Upon touching a key, they give off a small "ping" and slowly fade away. Sometimes, they are found inside cages and other times they float in open areas.
Castle Keys locations
Castle Key #1
After running down the first ramp and bouncing off the Wide Spring, the player will see Castle Key #1.
Castle Key #2
Grind the rails after the castle is turned upside down and then, after the player flies off, land on the platform. When the platform rises, fly to the top. After that, fly from the path the glowing spider symbols is pointing to, to get onto the next tower. The Castle Key #2 is underneath the upturned platform the player reaches.
Castle Key #3
After returning to the location the first key was in, go through the opened door. Turn invisible and run past the Egg Knight to get Castle Key #3.
Castle Key #4
From the third key, at the end of the room, jump onto the platform. It will rise upward. When the players jump off the platform onto the ledge, jump on the rail so that the playable characters go to the top. At the end of the path will be the Castle Key #4.
Castle Key #5
After touching the orb from the fourth key, look underneath the upturned platform for the Castle Key #5.
Castle Key #6
Jump into the Warp Flower over the upturned platform while invisible as Espio. When the player emerges on the other end, sneak past the Egg Pawns and the Egg Knight to get the Castle Key #6.
Castle Key #7
Just before the Egg Bishop's platform, touch the switch on the back platform. Then destroy them and use the Orb switch. Once the orb has placed the player somewhere else, turn around and get the Castle Key #7.
Castle Key #8
When the player reaches the invisible path after the seventh key, walk forward until the player has to go right, then use Charmy Bee to fly over to Castle Key #8.
Castle Key #9
After getting in the vicinity of the three robots just after the door beyond the eighth key, destroy them. After they are destroyed, break the wall in the back and collect Castle Key #9.
Castle Key #10
When the player reaches the final section of the stage, the Castle Key #10 is there on a platform just before the Warp Flower that takes the player into the beginning of the stage.
↑Guess, Gerald (6 January 2004). Sonic Heroes: Prima's Official Strategy Guide. Prima Games. p. 123. ISBN 0761544496.