The long distance institution of Igbo religion was the oracle. Ibini Ukpabi at Arochukwu, known in colonial writing as the Long Juju, arbitrated disputes for communities across the region and was reached by pilgrimage. The Aro traders who controlled access to it built a commercial network on that authority, and their involvement in the slave trade is why the British destroyed the shrine in the expedition of 1901 and 1902.
Christianity spread through Igboland from the later nineteenth century faster than through most of Nigeria, and today the great majority of Igbo people are Christian, with Anglican and Catholic churches long established and Pentecostal ones now prominent. Chinua Achebe's fiction is, for many readers, the only account of the older religion they will ever meet, and it is a novelist's account of the moment it broke.
The older practice has not ended. John McCall's ethnography of Ohafia records masquerade and dance traditions carrying historical knowledge into the present, and the ancestral cult, the ozo title system and the annual new yam festival continue in forms that sit alongside church membership rather than in opposition to it. Odinani, as a named and consciously revived religion, is a more recent development, and describes itself as a recovery rather than as an unbroken line.