As for how William managed to ambush next to the Pendant Box in advance, naturally, we have to go back to his previous Plan B... or was it Plan C?
By using the fragment of Voldemort's soul within Nagini, he achieved a reverse hacking.
— Just as Voldemort could project imagined images into Harry Potter's mind, Voldemort could do the same to Nagini. In fact, because the latter was a Soul Artifact that Voldemort consciously created, he had strong control over Nagini.
Strong enough to control her actions.
Of course, only the real Voldemort, who had been "shredded" by William's design, could achieve this.
And William's plan, which sounded simple, was actually difficult. This required Nagini's steadfast willpower, and all William could do was provide Nagini with a "bridge" that could serve as a battleground and use strong inducive potions to weaken the fragment of Voldemort's soul.
The battle could only be described as brutal. Nagini even repeatedly fell into dangerous situations where she was at risk of being devoured by Voldemort — but the result was gratifying. William, in Nagini's mind, successfully forcibly "tore open" a "backdoor" leading to the "global shared soul network" of Voldemort, casting Nagini's soul as a "virus" into it.
Yes, reverse possession.
Through this, William successfully pinpointed the locations of all the Soul Artifacts. He even determined that there were exactly seven Soul Artifacts that had existed — excluding the destroyed diary and the fragment in Harry's mind, four of the remaining five Soul Artifacts, including the Pendant Box, were in William's possession. Only the Hufflepuff Golden Cup was still out there.
But... William doesn't know if this counts as an advantage, as even now, he's unsure of what the other side actually wants to do with Voldemort's Soul Artifacts —
But it doesn't matter, even if he doesn't know — someone else surely does.
The smooth stone wall silently slid aside, revealing a staircase that spiraled downward into darkness, faintly smelling of magic potions. After dinner, having coaxed Hermione to sleep, William stepped down, quickly disappearing into the darkness. The wall silently closed behind him, leaving no trace.
At the end of the stone steps was a cold, eerie stone chamber.
It unmistakably looked like a lair for an antagonist, very stereotypical and very villainous.
The air was thick with a strong, choking smell of a sulfurous, viscous magic potion. In the center of the room was a giant stone basin filled with thick, emerald-green liquid.
Helbo's body was completely submerged within, with only a pale, twisted face emerging from the surface. His limbs and torso were wrapped in black bandages soaked in potion, glowing with an eerie blue rune. His eyes were also tightly covered with thick, potion-soaked black cloth strips.
The emerald-green potion emitted a barely audible but continuous "sizzling" sound, as if countless venomous insects were gnawing at the flesh within.
This was an instrument of torture William had designed, inspired by and modified from the Man-Qing Dynasty's top ten tortures, specifically targeting those not afraid of death.
Modified by Snape — indeed, after William casually proposed the requirement, Snape produced this inhuman potion within just two and a half hours. One must admit, these dark-hearted fellows have an innate talent for torment.
This potion continuously erodes the skin, muscle, and magic power of the body immersed in it, causing an itch deep in the bones and soul, but at the same time, the potion itself contains a strong healing ability, forcibly regenerating all eroded skin and muscle —
which leads to unbearable pain.
The cycle of destruction and repair is endless, completely eliminating any possibility of Helbo using suicide or death to escape.
At this moment, William's footsteps were exceptionally clear in the silent stone chamber.
Almost instantly, Helbo's body began to thrash violently. His pale, dry lips trembled fiercely, uttering broken, rasping, despair-filled howls and pleas of despair, echoing chillingly within the stone walls —
"William, Richard... please, please, sir! Stop, I'll do anything, please..."
He couldn't even form a complete sentence. This mental torment, conducted for less than eight hours, had already softened this ancient creature, who had witnessed millennia of grandeur.
Yet William showed no reaction, merely walking expressionlessly to the edge of the stone basin, looking down at Helbo's futile struggling and desperate wails in the potion —
This god of commerce and fraud, Hermes, whose pleas and cries were filled with maddening despair, made this self-proclaimed god appear utterly pathetic.
"Stop?"
A gentle curve appeared on William's lips, but his voice was calm, lacking the slightest wave, "Mr. Hermes, do you misunderstand me? In your eyes, am I someone with a soft heart?… Well, lift up your hand." Seeing the other unable to utter half a word, William raised his magic wand, gently touching the edge of the stone basin.
At that, an Alchemy Dragon Head embedded above the stone trough automatically opened, and a more viscous, dark green potion with a stronger corrosive aura poured down from it.
The emerald-green potion flowed out through a hole at the bottom of the stone trough — to maintain efficacy, the potion needed to be replaced promptly. As the fresh potion touched the skin, the "sizzling" intensified dramatically.
The next moment, Helbo let out an inhuman scream of extreme pain, his body twitching spasmodically but unable to move due to the restraints.
"You demon!!! No, Master William! Please, please let me go, I'll tell you anything — anything you want to know..."
"Enjoy your 'treatment.'"
William's voice, like a cold snake, slithered into Helbo's chaotic, crumbling consciousness, "Don't rush, Divine Envoy, we have plenty of time in the future. There's really no need to divulge everything so quickly. Trust me, you will absolutely love this feeling... Tomorrow, I'll come chat with you again."
Finished, he ignored the more intense, despair-filled, incoherent cries, curses, and pleas coming from the stone trough, leaving the room directly.
Exiting the Secret Chamber, breathing the fresh air, William couldn't help but shiver — truth be told, despite having witnessed many grand scenes, that sensation just now made him question whether he might be a bit of a psychopath — but to ensure the veracity of the information he subsequently received, he had to make sure this fellow dared not utter a single false word.
Though uncertain about where this guy's psychological defenses lay, being somewhat a "God"...
perhaps a week-long soak will do for now?