 The concept of "Chúkwú" ('supreme chi') was largely propagated by the Aro-Igbo of Arochukwu in eastern Igboland who wielded much spiritual force over the eastern Niger Delta in the 18th century due to their operating of the Ibini Ukpabi oracle.Lesser spirits known as "ágbàrà" or "álúsí" operate below the high God Chineke and are each a part of Chineke divided by gender in their mind.These spirits represent natural forces; agbara as a divine force manifests as separate alusi in the Igbo pantheon.