A sphere shape machine that hovers in the air, product of Gem. Co.. It’s only command is to search for Khalei Crystals. They search and collect the Khalei Crystals to bring it back to Gem. Co. Headquarters. It’s known to never hurt people in Rotarus. However it can attack any person for having Khalei Crystals on them self.

Gem. Co. can remotely use Sentinels to spy on people. And can Manually attack people with a laser beam. It’s unknown what the colors of the lens on the sentinels mean. People in Rotarus reported seeing these machines having different colors of Lens. Some even said it witness attacking people. However Gem. Co. denies the machine ever attacking people, it’s only command is to collect Khalei Crystals.