The Shadow Alucard mode was, in essence, the complete "Release" of the technique Blood Inheritance.
While Blood Inheritance infused Alucard with a specific individual's power system or combat advantages, be it strength, speed, or unique abilities, he typically used it with restraint. Most often, he utilized Red-Haired Shanks' Spirit of All Things, occasionally pairing it with Enel's Rumble-Rumble Fruit abilities.
Think of Blood Inheritance as having a safety switch that controlled the flow of power; Shadow mode was the total destruction of that switch, forcing the entirety of that power into Alucard all at once.
Alucard commanded two distinct "rivers": the River of Death and the River Styx.
The River of Death preserved the physical body, while the River Styx preserved the soul. One was for combat; the other for augmentation.
High-level powerhouses like Shanks or Sakazuki, when kept within the River of Death, were nothing more than mindless berserkers, pure power without reason. To remedy this, Alucard could extract a portion of their soul from the River Styx and reinject it into the body within the River of Death. This granted them a degree of intelligence, allowing them to recover the mastery they held in life.
However, the more power he infused, the more dangerous it became. Reshaping a soul back into a body carried a risk: if the infusion went too far, the entity might stop obeying orders. They could regain their own consciousness and turn their blades back toward Alucard, their killer. Furthermore, Alucard only had one life while actively manifesting the River of Death.
The destruction of the Blood Inheritance safety switch carried a similar risk.
If the power surge was too violent, Alucard himself would fall under the influence of those souls, particularly the fragments of souls tied to Devil Fruit abilities. While non-users like Roger or Shanks were manageable, the more Alucard used the powers of Zephyr, World, or Sakazuki in Shadow form, the more susceptible he became to their influence.
He had only maintained the state for a short while, yet his body already felt rebellious. The Devil Fruit powers within him seemed to reject him, scurrying through his veins like panicked rats, refusing to be harnessed.
Troublesome enemies are right in front of me; it's better not to use this form for now, Alucard thought. Since he couldn't perfectly control it yet, he decided to discard it.
As the years had settled upon him, he had grown closer to the original Alucard, but with one major difference: he did not seek death. He wanted to live, even if he often complained of being bored.
Alucard reverted to his usual appearance, a man in his twenties with a long red coat and a signature top hat. Seeing this, the three Gorosei narrowed their eyes. It really was Alucard.
Then what was the deal with the girl and the middle-aged man from before? Had it been one person all along? Or was it some unknown method of substitution?
"Now then, what method should I use to finish them off?"
Alucard's gaze shifted between the three Elders. If they all shared that mysterious power, he was facing three opponents who transcended the Yonko level. Even if the remaining two were weaker, they wouldn't be far behind.
He wasn't worried about anyone outside the Gorosei possessing this power. It was clearly a peak power system of this world; men as arrogant and paranoid as the Gorosei would never share it, even with their most trusted subordinates.
Alucard couldn't say for certain if he would win or lose against five Yonko-level combatants simultaneously as he had never tried it.
"Alucard the Immortal isn't someone who can be dealt with in a few moves," the long-bearded Elder began, initiating the situational analysis he was famous for. "Overusing that brings us no benefit, but he doesn't look like the type to just leave quietly either."
"Then your meaning is..." The curly-haired Elder with the cane had an inkling of the plan.
"Activate the National Treasure. Five percent should be enough."
As the long-bearded Elder spoke, the ground began to tremble violently. A colossal serpent, which had been circling the heart of Mariejois, surged out from the blood pool. Compared to a human, the size difference was like a blue whale to a speck of dust.
Alucard's True Ancestor Familiar: Jormungandr.
Snap!
Encircled by Jormungandr's massive coils, Alucard snapped his fingers. The serpent's head, large enough to blot out the sun, unhinged its jaws. Deep purple venom began to spray down like a waterfall.
"A single drop of this venom can kill a swarm of Sea Kings," Alucard sneered. "If even a bit touches you, you're finished."
"Is that the giant snake from the CP reports? It's as exaggerated as they said."
The curly-haired Elder, who had yet to act, finally moved. Golden light coalesced in his palm. With a sudden release, a golden vortex reappeared, instantly sucking the three Elders inside.
A portal-like ability? Alucard speculated as the golden swirl dissipated.
He turned his head to the right. The Holy Land of Mariejois was still there; although the battle had caused significant destruction and they had drifted some distance during the fight, they weren't too far away.
"Where else could you possibly go?"
Alucard vanished, reappearing atop Jormungandr's head. The giant serpent simply straightened its body slightly, cutting the distance to the city in half.
Recalling the conversation of the three Elders, Alucard muttered to himself, "National Treasure? Is it a panda?"
Meanwhile, in a hidden chamber within the Holy Land, a room filled with dense, circuit-like devices, the golden vortex appeared. The three who had just vanished stepped out.
The other two Elders had been waiting for them for some time.
"Even the three of you combined couldn't take him down?" the curly-haired Elder with the cane asked, frowning.
"Activate the National Treasure. Wipe Alucard out in one strike."
"Are you joking?" The blonde, short-haired Elder was shocked. "The last time we used it... I don't even know how many years it's been."
"Five percent is enough. I can't guarantee it will kill a man called 'Immortal,' but it should blast him out of Mariejois. He won't dare return anytime soon."