Gate Key

Gate Key is a special key that appeared in Sonic Adventure 2 and Sonic the Hedgehog''. ''It is simply a regular key that comes in various shapes in games.

Description
Gate Keys are special keys that have a dome in it's head connected to a star-like object in it's below in Sonic Adventure 2. In Sonic the Hedgehog, it has the appearance of the Special Key with a star on it's head. In gameplay, They have the ability to open gates and they're usually seen scattered around the stage.

Sonic Adventure 2
In this game, it usually seen nearing the gate and the player has to pick it and place it on a round location on the ground which has a hole identical to the Gate key appearance in it's center. Sometimes the Gate key cannot be seen nearing the Gate and the player has also to find, pick and place it in the Gate Key's place to open the gate. They can only be seen in Pyramid Cave.

Sonic the Hedgehog
In Sonic the Hedgehog, the player can only see and use the Gate key in the Shadow's version of Kingdom Valley and some of the hard stages where the player has to just find three keys that are scattered around the stages and the gate will open automatically. In this game, the Gate Key comes in three keys instead of one singular like Sonic Adventure 2 and they usually collected by the assistant characters that helps Sonic, Shadow and Silver instead from the heroes themselves. Those Gate Keys are usually found in Cases or behind breakable ice.