From Sonic Retro
The Combi Confiner, also known as the Combi Catcher (コンビキャッチャー), is a diabolical machine developed by Dr. Eggman, and deployed by the mad scientist in Newtrogic High Zone during Chaotix. The device appears capable of placing its unfortunate captives in a state of suspended animation, which (according to the US manual) can only be negated using Ring Power.
Knuckles first comes across the Combi Confiner at the very start of the game, in the dawn section of Isolated Island. The echidna stumbles upon Eggman as he tinkers with the controls of a mechanical pod containing a frozen Espio the Chameleon. The Doctor bolts when Knuckles approaches, and is bourne away by Metal Sonic. After freeing the chameleon from his imprisonment, Knuckles and Espio continue on towards Newtrogic High.
Here lies the Combi Confiner proper; functioning as part prison, part claw-grab game, Eggman's machine holds the anthropomorphic members of Chaotix (along with multiple copies of the robots Heavy and Bomb) in-between standard stages. The player must pick out a chosen partner using the grab-claw within the time limit; the selected character is then deposited in a pod to be thawed out of stasis.
The fate of the Combi Confiner after the battle against Metal Sonic Kai at the end of Chaotix is unknown; Eggman does not seem to have reused the stasis technology in any of his subsequent schemes. However, a similar capsule is used to contain Mighty and Ray at the beginning of Encore Mode in Sonic Mania Plus.