They believe in the eventual restoration of the Netherworld. The name "Ranthen" is derived from "amaranth" as it is the only flower that grows in the Netherworld. According to Warden, their call to arms was the blooming of the amaranth in Sheol I.
The Ranthen don't even make up a quarter of the size of the Rephaim who are loyal to the Sargas. There are two hundred of them, but only a few are on this side of the veil. Meanwhile, thousands support the Sargas.
After the failed rebellion of Bone Season XVIII, the Ranthen were tortured and scarred as punishment for their transgressions. These scars remain painful, and they are particularly known for drinking wine to dull the pain of the scars. While the Ranthen are willing work with the human clairvoyants to bring down Nashira, they are still prejudiced against humans, and disgusted by the thought of an intimate human-Rephaite relationship.