The gates of the Black Serpent stronghold cracked with a shriek that rattled bone and soul alike. A blast of green fire tore outward as the colossal obsidian doors split, belching black smoke and serpentine energy.
When the haze cleared, the strike force stared into the abyss. The fortress interior wasn't made of stone — it was alive. Veins of pulsing flesh ran across the walls, rib-like spires arching overhead, and serpent runes glowed like beating hearts. The air itself tasted of venom.
Professor X's voice pressed into their minds, steady but grim:
What lies beyond this threshold is not just their home. It is their god's cradle. Steel yourselves.
The First Breach
Juggernaut bellowed and charged first, smashing through the final shards of the gate, with Vanessa and Luna Snow tight behind him. The moment they crossed, tendrils of blackened flesh lashed out, wrapping around Juggernaut's arms. He roared, ripping them free — but more tendrils sprouted from the walls, dragging soldiers into the darkness.
"Cut them loose!" Captain America barked, hurling his shield to sever the living bonds. Wolverine dove into the mass of tendrils, claws flashing in a blur of silver, while Candy darted in and out, her claws tearing clean cuts between ensnared allies and the walls.
Still, the fortress fed on their presence, its glow intensifying with every life force it touched.
Hall of Echoes
The heroes pressed forward into a massive chamber — a cathedral of serpents. Pillars shaped like coiling snakes twisted upward, their eyes glowing green. The chamber whispered with voices, thousands at once, crawling into the minds of all who entered.
Jessica stumbled, clutching her temples. "It's… it's every doubt I've ever had—"
Varisa caught her, a gust of wind knocking the whispers back for a heartbeat. "Ignore them. They're lies made flesh."
But even Thor's jaw tightened as he heard whispers of Asgard's doom, and Natasha's eyes flickered with memories of blood-soaked missions past.
Only Professor X's telepathic voice steadied them:
They seek to fracture you with shadows of yourselves. Hold fast. We march as one.
With that, Delilah raised her hands, summoning a fire tornado that scorched through the chamber, silencing the whispers long enough for the strike force to advance.
The Bloodfall Bridge
Next came a narrow bridge of bone stretching across an abyss that pulsed with glowing green ichor — a river of venom. Above, serpentine spirits circled, shrieking as they dove.
"Everyone, shields!" Susan Storm cried, projecting wide barriers as arrows of dark energy rained from above.
Jessica extended her own barrier alongside Susan's, the twin shields reinforcing each other until the bridge itself trembled under their combined force.
But halfway across, the bone cracked. Segments fell away, sending Serpent soldiers and two SHIELD troopers screaming into the venom river below.
Varisa threw out her hands, creating gusts of wind strong enough to lift allies to safety. Baymax hovered forward, deploying grappling hooks to secure others.
Still, the Serpent spirits pressed harder. It was Vanessa who stepped forward this time, her body riddled with spectral blades — only for the wounds to vanish instantly as the damage rebounded onto the spirits themselves, dissolving them into nothingness.
The bridge held. The heroes crossed.
The Heartbeat Chamber
Finally, they reached a cavern where the walls pulsed like lungs, the ceiling dripping ichor that hissed when it struck the ground. At the chamber's center rose a massive black crystal — the fortress's core, its heartbeat.
"Looks like the power source to me," Tony muttered, scanners flickering red. "But something tells me it's not gonna let us unplug it quietly."
As if on cue, the crystal pulsed violently, and from its surface slithered three Serpent Generals, each larger and more grotesque than before, their bodies forged of steel, scales, and sorcery.
The ground shook as they drew massive weapons — a spear, a chain, and a sword so large it dragged sparks across the floor.
"Avengers—assemble!" Steve roared.
"X-Men—hold the line!" Cyclops shouted.
"Thunderbolts, you know the drill!" Moonstone snapped.
In that instant, the fortress erupted into chaos once more. Fire, blood, lightning, wind, ice, and steel clashed against the Serpent Generals in a storm of impossible violence. The crystal pulsed harder, as though feeding on the battle itself.
Above it all, Xavier's voice echoed:
The heart of the serpent lies ahead. But beware—the closer you draw, the deeper its fangs will sink.
The true battle for the world had begun.