Carnelian Signet

The Carnelian Signet is an explosive which makes its first and main appearance in Final Fantasy IV as a key item. The item is named Bomb Ring in releases prior to the game's 3D remake.

Final Fantasy IV
In Final Fantasy IV, the Carnelian Signet has a role at the start of Cecil's adventure, and is the first key item that he obtains.

At the start of the game, the King of Baron revokes Cecil's rank as Red Wings commander because Cecil questioned why he had them kill innocent civilians for the Crystals. The King of Baron instead sends both Cecil and Kain on a mission to deliver the Carnelian Signet to Mist. Once they arrive there, the Carnelian Signet goes off by itself, causing Bombs to release and put the entire village on fire. Cecil and Kain realize that the King had duped them into killing the summoners living there.