Prism Beast

The Prism Beasts were constructs created by the rogue time traveler Sarko, the future son of  Soranik Natu and Kyle Rayner.

Design
The Prism Beasts were green crystalline constructs made of pure willpower. They were created using Krona's Gauntlet an artifact that could tap into the Green Spectrum of Light without the need of a Green Lantern Ring. The Beasts were immune to all attacks from the Green Light as well as the Yellow Light. Sarko in order to preserve his existence conditioned the Prism Beasts to not attack his parents.

History
Sarko having developed an obsession for his maternal, identified with his use of fear as a source of power to bring order to the cosmos. Disgusted with his parent's position as Green Lanterns, he opted to travel to the past to the point where the Sinestro Corps allied themselves with the Green Lantern Corp and change history to resurrect the former.

He utilized constructs made of pure willpower, leaving the Green Lanterns and even the Yellow Lantern unable to harm them with their rings. A major weakness was found when the Prism Beasts were harmed physically without the rings allowing the two Corps to defeat them.

Source

 * Hal Jordan and the Green Lantern Corps 18 (2017)
 * Hal Jordan and the Green Lantern Corps 19 (2017)
 * Hal Jordan and the Green Lantern Corps 20 (2017)
 * Hal Jordan and the Green Lantern Corps 21 (2017)