Cinnabar

Cinnabar is the only Gem who goes on night patrol. Due to their body producing a poison (Mercury) which is harmful to Gems and living things, they are isolated and ashamed of themselves. They hate fighting and hate to be seen. According to Rutile, Cinnabar has an extraordinary amount of talent and combat ability, but is too much to handle due to their uncontrollable poison that ruins everything it touches. Cinnabar's silver poison gathers faint light at night, which keeps them awake and aware while night patrolling. According to Kongo-sensei, the night patrol is something Cinnabar came up with by themselves. They used to spend their time during the day in Hollow Cape waiting for the Lunarians to take them since they thought they may at least be of use to them. They are knowledgeable about things other Gems don't know and was recommended by the Gems for Phosphophyllite's work on the encyclopedia. After accidentally hearing their secret and wish, Phos promises to help Cinnabar find a job more suited to them than night patrol, "a fun job only they can do". They have a red color scheme and wear the winter uniform year-round. They wear black oxfords and sometimes black gloves when touching something, but no socks. They have a medium length, asymmetrical haircut with a longer section that hangs in front of their face. They have a cowlick in the anime. Cinnabar is gloomy and hates themself for dirtying the things around them with their poison, though they are outwardly aggressive and dispassionate towards others. According to Kongo-sensei, Cinnabar is far too wise and too kind to be alone. Although they try not to show it, they have a tiny sliver of hope that Phos will be able to fulfill their promise. They are depicted as being intelligent and mindful of things, able to provide Phos with some information they needed for their encyclopedia. Cinnabar also seems to have a form of social anxiety, as in Chapter 65, they have a hard time talking to Kongo-sensei as well as their fellow gems. When encountering Phos each time, they seem doubtful of their words and outwardly annoyed with them, even going so far as to run away at one point. But they are the only gem they regularly speak to, with even Diamond only coming by sporadically. After the 220-year time skip, Cinnabar is shown to be much happier and returned to live at the school, though they still find it difficult to talk with others. They seem to have a close bond with Bort.