Later, Hades will look back and realize everything before him was a product of his own desires. His own wishes. Because within the Pantheon, the whims and wishes and wills of the Gods hold a power all their own, and even long beneath the darkness of the earth it holds true. An off-shoot from their birth in a time of Chaos, a power that refused to simply fade away into obscurity like their progenitor.
For now however, Hades rages. He rages, even as he furiously scribbles away at his work, keeping burning eyes to his desk, to the names and dates before him. His son is willful and arrogant and so damned determined to see the light of the sun, to chase after the fading echoes of a mother that doesn't exist. Persephone left, and Hades let her go because he knew better than to try to keep her. To try to stop her. He fought that battle once, and he was not prepared to fight it again.
He puts obstacles in Zagreus' path, and Zagreus merely hacks them down and keeps going. Varatha sings his in hand - all the Titan-slayers do, now, but Varatha most of all, and how terribly ironic it is - ready to make war all over again, and loyal to her keeper as he continues to ascend. The shades of the Underworld are wary of him, now. Everyone has seen the strength of him, the terrible wrath he brings as he quests ever-upward.
Hades has already repelled him, once. In that terrible place of ice and biting winds, the taste of sunlight and earth just mere moments above. A place not meant for the dead, for the Underworld. Zagreus does not appear to remember it. The fight was brutal, and Hades himself was inches away from oblivion, but Zagreus' foot had slipped, and he'd stumbled right into Hades' next thrust, and Hades had speared him to the earth. He'd died there, looking up at the sky, blood slicking his lips and chin. Hades had watched as the light fell away from his eyes, and his body evaporated, sent back to the pits of Hell were it belonged.
He cannot know. He cannot know, just as the Olympians should never have been made to know. Because if he were truly Persephone's son, it would be one thing.
But he isn't.
He is Hades' son, and no one else's. He is Life and Blood, and Determination. But all that too, is in Hades. Deep, untapped, neglected because Hades saw no point in rearing the power of Life when others already had it. It manifested when Zagreus tore himself out of Hades' chest, when his wails rent the air.
He remembers, still, the moment the chest pains he had been experiencing deepened, worsened. He'd been sitting on the edge of his bed, rubbing one hand across the space where the ache had slowly been digging, and he'd felt something reach back.
A split second before it had happened, he'd known. A cold realization.
What I would not give for a son, to inherit all my power. An heir. A child of some sort.
Gods' whims and wishes and wills are powerful things.
Zagreus had lain next to his heart for a year, being born in a rare way, and when he'd been ready, he'd pushed against Hades' ribcage, and clawed his way through the meat of his chest, and out. And Hades, unable to die, had caught him as he'd come out, covered in blood and wailing, a shock of darkest hair upon his head. The wail had been loud, and Persephone had come running.
He still remembers the look on her face, standing there in the doorway, staring at her husband, who held little Zagreus in two massive hands, mouth open with shock as he'd held his child.
His child. His, and no one else's.
Part of Hades wants to tell him. Wants to go to Zagreus in a quiet moment, and peacefully tell him the honest, painful truth. That he was born in blood, born of Hades' desire for a child, and that was its own power. That his home is here, in the dark, and Hades his only parent.
But he is proud. He thinks it fitting that Persephone chased after something that did not exist, and left when she could not find it, when reality left her feeling cold and hollow and cheated, and now Zagreus is doing much the same. Except when he discovers the reality, when the Olympians discover the truth, it is not into the sun he will flee, but back home.
Back home, into the dark, back to the House of Hades, and back, at last, to his birthright.