"I know you're upset..." -RGB
Griefs are a type of creature seen only briefly in The Property of Hate. The first and only time we have seen one is in Chapter 6, where it came to drown RGB in the Plains of Hesitation, before being driven off by Negative.
Griefs are very large, and thus their entire shape is difficult to distinguish. They appear to be made of stone and veins of fire, while water pours from what appear to be eyes.