Unnamed Cult Leader was The Leader of The Cult Of The Spence and he worshiped Spencer until he sacrificed himself to be possessed By the Spence. It can be assumed that he is a Higgilydiggilyhögen clone as Spencer later states he is a Higgilydiggilyhögen clone (and they technically are the same person).
Unnamed Cult Leader worshiped the Spence and sacrificed himself to be possessed by The entity. However who Spencer behaved was not at all how he described him. Whether the cult leader was tricked or mistaken, or the Spence's possession of him somehow changed the entities personality all together is unknown.
Unnamed Cult Leader became good friends with Gas Mask Cult Member.
Unnamed Cult Leader became good friends with Shirtless Cult Member.
Pokemon Obsessed Cult Member was new in The Cult and Unnamed Cult Leader hated him ( Mostly Because he was annoying.)