The Special Stage Key (スペシャルステージキー Supesharu Sutēji Kī?), also called the Special Key, is an object that appears in the Sonic the Hedgehog series. It is a golden, sparkling key that allows entrance to a Special Stage once collected.
In Sonic Heroes, the Special Stage Keys can be found in various locations of the Stage where it is usually contained in a Cage. The player can collect the Special Stage Key by simply having the leading character touch it. Once the Special Stage Key is collected, its icon will appear in the HUD on the top-left corner of the screen. After completing the stage, the team is taken to the Special Stage. If the player is attacked (except if the leading character had a Shield upon being attacked) or loses a life (e.g. falling into a bottomless pit), the Special Stage Key disappears. There are no Special Stage Keys in Super Hard Mode.
Sonic Advance 3
A similar key item called the "Special Key" appears in Sonic Advance 3, which appears in an Act of a zone after the player has found all ten Chao from that zone. Most Special Keys tend to be located near the start of the Act. Once the key is collected, it will appear in the HUD. After the player clears or quits the Act, the collected Special Key is added to the total number of Special Keys in the player's possession displayed in the HUD while in the Zone Map. The player can only hold a maximum of nine Special Keys at a time. The player can then jump onto the locked Special Spring on the Zone Map to enter the Special Stage which consumes one Special Key in the process.
- In the early versions of Sonic Advance 3, the Stage does not need to be finished; the players could just exit the stage while retaining the Special Key in their possession.