The Zurr flourished between the time of the Great Collapse and the present era. The Expanse is named for them, though how much of the territory their civilization actually controlled is a matter of debate.
The zurr are only known from their iconography (images of tall humanoids in unadorned, flowing robes and elaborate, non-representational masks), some ritual sites with oddly angled monumental structures, and a few apparently functionless artifacts. Mysteriously, they left no information technology or tools necessary for an advanced civilization behind, but their presence is attested on multiple worlds. They are blamed for unleashing the Ssraad upon the galaxy.