WARNING: The following contains spoilers for Episode 1 of Onyx Equinox "The Last Day," now streaming on Crunchyroll.
The premiere episode of Onyx Equinox, Crunchyroll's latest original series, introduces viewers to a mythical ancient Mexico where the gods battle it out in brutal fashion, with their innocent devotees caught in the middle. But no one is more trapped in their wake than the young Izel, who makes the ultimate sacrifice and becomes a pawn in their cruel game.
The episode opens on a bustling city in the middle of its day. People mill about, shopping at the market, moving to and fro, baskets in-hand or on-head. In one corner of the town, a young woman, Zyanya, trains in a sparring match. She easily pins her partner -- just before the sky suddenly goes red and a warning horn blares. According to a messenger, a recent sacrifice failed, and trouble is on its way.
As tremors rock the city, Zyanya runs to find her parents, just in time to see her mother swallowed whole by emerald slime rising out of the cracks in the ground. Slime rises and consumes people all over the city, coagulating into monsters that rip bystanders to shreds. The only thing the citizens have to defend themselves against the monsters is an obsidian obelisk just outside of town that burns the beasts when touched — but it's not nearly big enough for everyone. Zyanya leads as many as she can to the obelisk's grounds, but more people are caught on the way.
Standing atop one of the city's pyramids, a priest slits his throat as a desperate offering to the gods. The pooling blood rises from his dead body and flies off into the lands outside the city, summoning the gods Cocijo and Xoo. But it's already too late. The creatures gather in the city center and force their captives to slit their throats. The blood is absorbed into the earth and summons Mictlantecuhtli, the massive god of the dead. The titan grabs Xoo, rips them in half and drinks their blood as Cocijo flees. Mictlantecuhtli then completely obliterates the city, creating a gigantic pit where he stands. Zyanya, just outside the blast zone, clings to the obelisk as she watches her family and city plummet into the abyss.
As survivors run to escape the desolation, a child is possessed by what turns out to be the god Quetzalcoatl, who goes to meet with other gods possessing people — including his rival, Tezcatlipoca — in a burned-out hut. The gods discuss the appearance of Mictlantecuhtli and the "abduction" of the city. They take this as an act of war as, during a blood drought, the god of death is snatching sacrifices from the other gods. To rectify this, they resolve to close the five gates to the underworld, which would cut those deities off from the human world and leave more blood for everyone else.
Quetzalcoatl volunteers for the task, despite not being entirely on board, and Tezcatlipoca lets him know that, at the equinox, he'll begin the destruction of humanity so they can start over, citing humans' violent tendencies as a waste of blood that's starving the gods out. Not wanting to remake humanity yet again, Quetzalcoatl instead proposes a bet. Seeing as the Olmec tools that'd close the gates are made of obsidian, which burns monsters and gods alike, Quetzalcoatl will send a human to do the job in his stead. But not just any human — he'll send the most pathetic human out there. And, if they succeed, humanity will be spared and Quetzalcoatl will get Tezcatlipoca's blood sacrifices, which would kill him. Tezcatlipoca agrees, with the caveat that his emissary, Yaotl, guide the human.
Elsewhere, in the town of Uxmal, weaver siblings Izel and Nelli take their wares to market, where they encounter survivors of Mictlantecuhtli's rampage. The city's destruction is the news of the day and word is there'll be a sacrifice to prevent the same thing from happening in Uxmal. Izel and his sister are actually Aztec, making them outsiders in this Maya town and the first on the chopping block. The town elders suggest Izel, but Nelli volunteers to take his place, meaning she'll be sacrificed at sunrise. The two spend a final evening together with Izel none the wiser but, as the truth comes out, he races to offer his own blood so Nelli won't have to die.
But he's unable to do it, and Nelli is sacrificed. Devastated by the loss of his sister, Izel tries to end his own life and jumps into the same pit. But he hits his head on the way down, the blood summoning something from beyond (Quetzalcoatl?), which marks him as humanity's champion in the gods' game. Yaotl appears and rescues him from the pit, less than pleased that pathetic Izel is now the gods' gift to mankind. It's going to be an uphill climb for Izel, especially considering he's now meant to save a world he wants no part of.