Toroid (トーロイド?) is an enemy first appearing in Xevious, shaped like a metal ring that appears early in the game. It is easily destroyed by the player with your zapper. Later on, it gains the ability to shoot. Unlike the others, they are the least dangerous enemies in the game, unless paired up with others. Their movements consist of pulling away from the screen, firing a shot while doing so. In Xevious: GUMP No Nazo, there is an upgraded variant that resembles a letter "D" rather than a ring. This variant simply continues to fly in the direction it came from, firing when you come near it.
Notes
In Xevious Resurrection, there is a boss that resembles a gigantic Toroid with 4 red sectors and an inner ring with 3 red sectors.