Rinka

Rinka are small red or green rings of energy which thrive only in Tourian and can move through any surface, much like the Wave Beam. They are endlessly regenerated as they try to prevent Samus from reaching Mother Brain, showing them as a security system for the supercomputer. They are seen launching out of circular generators found on ceilings, floors and walls, though there have been times where they spontaneously phase out of surfaces without the use of said generators or even out of thin air. The green Rinkas are noticeably launched faster than the red variant. In Metroid: Zero Mission; if the Rinka are destroyed, they will provide Energy Capsules and Missile Ammo. In the original game and Super Metroid, they do not. After Mother Brain's destruction, Rinka are no longer generated throughout Tourian in Zero Mission and during the base's self-destruct sequence in Super Metroid. In Metroid: Other M, Rinka rings make an appearance in several passageways before Room MW, slowly homing in towards Samus as soon as they are shot from turrets resembling Ring Beam Units. They can be shot and destroyed. They make popping sounds each time they are spawned, and deal severe damage to Samus. These Rinkas, unlike their other appearances in other games, bounce off of any surface they come into contact with and can no longer pass through solid objects (for reasons unknown). However, this loss has made them into a greater threat; as they continuously spring away from a surface, they will always remain within the room (if not destroyed) and will persistently target Samus, which overall increases their chances of colliding with her. Their appearance foreshadows the approaching encounter with a certain someone. Though never confirmed, it is likely that they were also present in Sector Zero, a replication of the Tourian base.

An attack similar to the Rinkas appeared in Metroid Prime 3: Corruption, where Aurora Unit 313 had energy cannons surrounding it which shot red spheres that tracked Samus.

Metroid manual
"These fireball creatures suddenly appear in the last scene. Lots of them appear but they are not very strong."

1986 manga
"These fireballs suddenly erupt from the base's walls. They can be destroyed with the Screw Attack and Ice Beam."

Official Nintendo Player's Guide
"These are fire rings which appear unexpectedly. A maximum of three appear where Samus is located."

Super Metroid Nintendo Player's Guide
"Freeze them so no more will come out to get you."

Appearances

 * Metroid (first appearance)
 * Metroid (1986 manga)
 * Super Metroid
 * WarioWare, Inc.: Mega Microgame$!
 * WarioWare, Inc.: Mega Party Game$!
 * Metroid: Zero Mission
 * Metroid: Other M

Cameos

 * WarioWare, Inc.: Mega Microgame$! and WarioWare, Inc.: Mega Party Game$! has a microgame named Metroid that re-enacts the fight between Samus and Mother Brain in the first game. Rinka are found on the second and third levels. If they hit Samus, they will only make her shake.