Rancora is a world that Portal Keeper Hasabel opens a portal to during her encounter in Antorus, the Burning Throne. Hasabel describes it as "a landscape of festering pools and skittering death."
This article or section includes speculation, observations or opinions possibly supported by lore or by Blizzard officials. It should not be taken as representing official lore.
Since the demon who comes through the portal, Lady Dacidion, is an aranasi, Rancora may be that race's homeworld. Hasabel's description of the world also fits what is seen of aranasi territories, so at the very least they are a prominent presence on it.