Ezekiel "Zeke" Sáenz, also known as the Black Diamond, is a member of Jaxon Hall's clairvoyant gang, the Seven Seals. He is an unreadable, a rare type of clairvoyant. He is the older half-sibling of Nadine Arnett.
Little is known of Zeke's life prior to joining the Seven Seals. He was born in Oaxaca, Mexico. He lived in multiple cities, but at some point moved away to live with his half-sister Nadine in the United States. In 2057, he travelled to the Scion Citadel of London with her on a college trip to find out more about the Scion system. After the pair were approached by Jaxon Hall, they elected to remain in the citadel to learn more about their clairvoyance.
Zeke was in many of Paige Mahoney's flashbacks while she was kept in Sheol I. For example, she recalls when Zeke asked her to sing the song An Ember Morning after learning Paige was Irish. Jaxon doesn't show any particular concern for Zeke's mental well-being. He experiments on Zeke by making the others attack his unreadable dreamscape. It is also heavily implied that Jaxon used false promises to get Zeke and Nadine to stay in Seven Dials.
Zeke agrees with Paige that they need to do something about the Rephaim.
After the scrimmage, Zeke and Nadine remain loyal to Jaxon.
Nadine and Zeke have been staying low in Seven Dials. However, Terebell Sheratan wants them gone because they are still loyal to Jaxon. Jaxon ends up helping them get out of London safely.
Nadine and Zeke travelled to France along with Jaxon who had betrayed them, selling them to the penal colony of Sheol II located in Versailles. They were later rescued by Paige who infiltrated Sheol II in an attempt to free all the prisoners, most notably her former associates and a potential ally, Le Vieux Orphelin.
After Warden was captured by Nashira Sargas, Paige arranged Zeke and Nadine's return to London in order to warn the Mime Order of Arcturus' supposed betrayal. Before leaving, Nadine and Zeke wished Paige good luck and acknowledged that they were now members of the Order.
Zeke is slim, with brittle wrists and tanned skin. He has eyes the color of black tea and a thin, restive face. Above his brow there is a vertical scar.
Zeke has a bit of an anxious disposition.