The “king” in question is no other than the Eze Nri in present day Anambra state which is located EAST of Benin.

It must however be noted that in Igbo civilisation, the word Eze does not refer to a “king”, but rather a high priest. The Eze is the highest level in igbo priesthood. Under the Eze are minor priests called Ndi Nze who are empowered by the Eze to adjudicate land disputes in their respective clans. This is a legacy of the agrarian era in igbo history. During this agrarian era, the agricultural societies in these parts all the way to Benin were under the Eze’s sphere of influence. The Eze also provided a key service to all the agricultural communities, namely pest control medicines, adjudication of land disputes and “control” of weather patterns. He was also the custodian of the 4 deities around which the days of the weeks were counted namely Eke, Orie, Afor and Nkwo. In Edo these are called Eken, Orie, Okuo and Aho. Another igbo concept found in Benin is the culture of personal strength called Ikenga, again a legacy of the agrarian era of Igbo history. Agriculture was so successful in Igboland and lead to a boom in population growth also notable in other areas of Nigeria where agriculture was successful.
Benin with its population is no match to the igbo population even after the war and starving to death of millions of igbo children by Obafemi Awolowo and his Federal government masters from the North.
Now, for an Eze Nri to emerge certain rituals are performed including the funeral of the candidate revealed by an oracle. After this funeral, the candidate then becomes a living deity never to be seen by anybody other than his attendants. This is why he sits behind a curtain and only his feet are seen, so the Benin ambassador was right to refer to him as a god Oghene because he was considered to be a living deity (still the case). As a matter of fact, his influence was still noticeable long after Nri as a civilisation had declined due to the rise of the slave trading centres such as Benin, Efik, Ibibio etc. so much so that the British hoping to put an end to this reverence of the Eze, forced him to appear in public for the first time at the Awka native court. In being told that the man in their presence was the Eze Nri, the assembled public fled.
All igbo clans and igbo speaking peoples are united by this shared civilisation dating back to the 9th century.
A burial site was discovered at the old capital of this civilisation, a place known as Igbo-Nkwo (now called Igbo-Ukwu). The artefacts in this burial chamber included an intricately design roped pot dated to the 8th and 9th centuries; this bronze artefacts predates any bronze artefacts ever discovered in Yorubaland and Edo state.
Another evidence of the reach of the igbo civilisation is the presence of igboid speaking peoples everywhere in this region, from lower Benue to Edo state itself (Igbanke), to Cross Rivers state (ISOBO), to the eastern parts of the Niger Delta (Ikwerre, Ndoni and so on) to Western bank of the river Niger (Enuani, Ukwuani, Ika), to Kogi state and so on.
The Nri civilisation with its main centre in the Nri-Awka axis was NOT an empire nor was it interested in building empires. Infact it had no standing army. It was a an agrarian civilisation that helped to create the laws that kept the peace amongst the agricultural people of this part of the world. It helped to define authority, and helped the agricultural communities make sense of their environment and sense of existence. That is why even when eventually the small town of Benin came in contact with the Portuguese slave traders and became a rich slave trading outpost, its rulers still needed to legitimise themselves using the only known spiritual authority which was the Eze Nri who presented ofor to all the various communities in the region.
In modern Nigerian politics, the people who are most despised yet also the people who everyone is secretly or openly obsessed with, are the Igbos. So it is fashionable to try to discredit the igbos. Most Nigerians don’t even know the richness and depth of igbo history because Igbo history wasn’t flattered by the British who tried their best to suppress it and promote centralised monarchs such as Emir, and Oba.