something something every child of the Big Three, after the oath, is cursed to die young—because that’s the consequence of their parents breaking it.
Jason couldn’t escape it.
Bianca’s wasn’t the curse, her fate was simply... that way.
Thalia found a loophole by becoming a Hunter.
Now Jason is dead, and the curse moves to its next target: Percy.
Poseidon knows about the curse (the Big Three all do, they just never told their kids), so he goes to Styx asking for a way out. Styx says the curse can be compensated—but only by compensating for the oath Poseidon broke, to Zeus and Hades. Zeus never upheld his side of the bargain, so that leaves Hades. To rebalance the broken oath, Percy must be bound to the Underworld in life, not death. Through marriage to a child of Hades, creating a living tie where a fatal one was promised.
So Poseidon goes to Hades and begs(demands) to let Percy marry into his family. Hades, who genuinely does not care, remembers that Nico once liked Percy. He agrees—so long as Nico accepts.
Poseidon then goes to Nico under the pretense of a “mission,” fully intending to be a wingman and convince this kid to marry his son. Nico(22 now) is like, nah man, that was a long time ago, I’ve moved on (he hasn’t).
As the mission goes on, Poseidon kind of grows fond of him?(like every god involved with Nico lol, even cupid was kinda fond in a way) From his perspective this kid is funny and sad and very low-key lonely. Poseidon ends up acting like a chill, but dumbass, overly powerful mentor to Nico.
One day Percy goes to visit Nico and walks into the apartment like, why is my dad in your apartment, dude?
Percy immediately assumes Poseidon is courting Nico—because gods—and if that’s true Percy is fully prepared to cut ties with his father and hide Nico somewhere God-proof.
Nico just says he’s trying to convince me to marry you.
And Poseidon finally confesses everything about the curse. Halfway through the explanation, Nico just says says I'll do it. I'll marry him.
Percy is still processing.
Poseidon is thrilled. He claps, hands Percy a ring, gestures for him to kneel, and says Percy should propose before Nico changes his mind.
Percy says actually, Nico and I need to talk. You go.
Cue Percy and Nico having that conversation. Angst. Arguments. Percy being furious at his dad for never telling him about the curse. That whole saving the world should have been enough. Eventually Nico admits he can’t lose Percy too—not after everything.
So he convinces Percy to agree to a platonic marriage.
And then begins the slow-burn hell of being married to the person you’re in love with while insisting you’re not. Nightmares about wishing the marriage were real. Being domestically, stupidly in love in everyone's eyes except their own.
It takes them three years to realize they are, in fact, actually in love—and that the marriage has always been nothing but the absolute truth.
Meanwhile Poseidon is under the ocean, humming softly because his son is alive, his sad little depressed kid is now his son-in-law, he and Hades are bonding as in-laws and backing each other up in Olympus meetings, and marrying sons of powerful domains turns out to be excellent move in Olympus politics.
Percy eventually forgives him for keeping the curse secret, because honestly, Poseidon was a great wingman.
