"Ba'ul" according to an interview jones gave to the hollywood reporter. the article specifies that the ba'ul are eating the kelpiens but i'm pretty sure that wasn't made explicit in the episode. "Mentioned but never seen, the Ba’ul are a race who feast upon the Kelpiens. The prey, in turn, takes this as a natural part of life, all to keep what is called the “great balance” and maintain the lives of those they leave behind. In fact, they’ve turned the recurring culling into a pseudo-religious ceremony. Led by Saru’s father Aradar (Robert Verlaque), the chosen few kneel in a circle of stones, as they await the bright light and noble ending that comes from their sacrifice. Spilling blood is such a norm on Kaminar that their sand is symbolically stained red."