Ion
Ion is the embodiment of willpower, born when life first moved of its own accord, and is connected to the green light of the emotional spectrum. Ethan Van Sciver describes Ion as resembling a large, primitive whale or fish. Representing the stability of willpower, Ion serves to support its host, providing a vast supply of power in return for the willpower provided by its host. This contrasts with Parallax, who dominates its host, controlling them in order to inspire fear in others. Ion is prominently featured in the "Sinestro Corps War" storyline, and is first seen when it is removed from Kyle Rayner. The entity itself has several physical characteristics emulated by the Guardians and their Corps. The Guardians' insignia appears in a pattern on the creature's dorsal side. Ion also has a monk fish-like appendage that ends in a lantern-like lure.
After being taken from Rayner, the Ion entity is held captive on Qward and experimented upon by the Anti-Monitor. Later rescued by a team of Lanterns, it is returned to the Guardians of Oa, who bond the creature with Sodam Yat (a novice Green Lantern from the planet Daxam) in order to form an "ultimate weapon" to combat Superboy-Prime.
Following its removal from Yat and captivity in Ryut, Ion is the second of the seven entities to be captured by Krona, who forces Ion to possess one of the Guardians of the Universe during Krona's invasion of Oa. Ion is eventually free from Krona's control, after Hal Jordan defeats and kills the rogue Guardian. Ion is once again at large in the Universe.
Read more about this topic: Emotional Spectrum, Emotional Entities