I stood at the mouth of the slope that descended into hell.
I reached my hands out as if warming my palms over a fire. The warmth did not oblige, and the undying night remained as cold as it had been for the past hour. I sighed.
It had been surprisingly easy for me to excuse myself from the Human Village. Marisa, Reimu and Miko assumed I would be at the bookstore, and as they had their own errands to attend to, they did not attempt to make sure I was doing what I was apparently supposed to be doing. The illusion was complete once I told Kosuzu that I had someone I needed to visit for the day; she thankfully did not probe further, and so all the proverbial loose ends were tied without much trouble. The journey back to Former Hell was undertaken in a straightforward manner as well – I trusted that, given that Suwako apparently had Kanako Yasaka's blessings in asking me to come here, I would not be spirited back into Senkai, or somewhere much worse – maybe the current manifestation of Hell (a logical conclusion given the presence of a "Former" Hell), or even the Moon. My trip to the underworld was thankfully unimpeded, and I arrived in the courtyard where I had stood just two weeks prior as a guest of the master of this palace, Satori Komeiji.
I arrived to find Satori Komeiji once again playing the obliging host, standing by the entrance to the Nuclear Furnace, nodding in greeting as I materialized.
"Welcome back, traveler," she said, smiling warmly.
"Thank you." A chill ran down my spine, but it was merely due to the frostiness of the surrounds that had laid claim to the courtyard. I rubbed my elbows, and Satori noticed my troubled features.
"Here, stand by me. It is much warmer here."
I stepped towards the hole and peered inside. A dim red glow emanated from deep within.
"Are Suwako Moriya and Kanako Yasaka here?" I asked.
"They are. Miss Yasaka is at the geysers – she will not be available for the time being. Miss Moriya should be coming up shortly."
A shadow stretched across the glow, and the tired features of the god atop the Mountain emerged.
"Thank you for coming, traveler from beyond." Suwako Moriya beckoned for me to enter. "Watch your step."
Satori and I gingerly descended into the abyss. As we followed Moriya into the depths, the color of the light began to brighten, transforming from a deep vermilion to a cheerier orange, punctuated by an occasional flare of lemon yellow.
"We are not quite at the Furnace yet, if you are curious," Suwako said as the heat began to send a different sort of chill down my spine. "This is what we call the Remains of Hell."
"The remains?"
"Look down below."
We found ourselves in a spacious chamber of rock, sloping unevenly towards a closed ceiling above us, and stretching downwards for untold miles into what appeared to be a broiling, searing bed of magma. The only thing stopping us from falling into the scorching hot abyss was a flimsy-looking metal walkway, held aloft by an array of thick pillars that pierced through the lava, seemingly unperturbed by the sheer heat that surrounded them. There were railings to prevent the unsuspecting from losing their balance, but even with those barriers it was difficult for any users of the passageway to feel entirely secure about making their way across the expanse, especially given the all-encompassing warmth that permeated throughout the chamber, giving the place the feeling of an uncomfortably dry sauna.
"The fires of Hell once burned day and night inside this room, punishing the deserving, and sometimes the undeserving." Moriya gazed impassively at the sea of molten rock. "But the genesis of Gensokyo also created an imbalance within the dimensional fabric of this space. Coupled with the burgeoning issue of overpopulation within Hell, it was decided that Hell would be transported to a more suitable location within the confines of Gensokyo's underbelly. So, the fires were doused, and the spirits who were doomed to burn for eternity were made to burn somewhere else."
"It still seems pretty hot to me," I commented.
"That is because we have reignited the flames. The Furnace can only serve its purpose as long as the Remains of Hell are still alive to power it. But its energy is no longer derived purely from the geothermal motivations of the Earth's mantle."
"Then what fuels the…" A thought suddenly struck me – a memory of a conversation I'd had with Marisa the last time we had come to the underworld.
"Corpses," I breathed. "Corpses power the Nuclear Furnace."
"I am surprised you knew. Though, given your proximity to so many of the realm's most knowledgeable figures, I suppose nothing of the sort should be so surprising."
"But surely that must mean a lot of corpses? I don't know the details, but that is a lot of biomass to go through to maintain such intense heat. And it doesn't seem like Gensokyo has enough bodies to go around."
"It is not the physical forms of the corpses per se that gives the Furnace its fuel." Suwako stopped and leaned over the railing, gesturing for me to do the same. "Look carefully. It is not only magma that inhabits the pit."
I peered into the lava, squinting as the searing light and heat burned flashes and shapes into my retinas. But just before I was forced to draw my face away from the fire, I noticed that whenever a flicker of lava rose from above the otherwise smooth exterior, it seemed to release a wisp of white smoke into the air that coalesced into a solid form and twirling around in the air before plunging back into the magma with a splash. Unusual, given what admittedly little I knew about how molten rock worked.
"That is a spirit," explained Suwako Moriya. "But not just any run-of-the-mill spirit. It is a vengeful spirit."
"A vengeful spirit?"
"Not quite a whole vengeful spirit, but the remnants of one. They are found in the corpses of people who have unfulfilled desires, or have been wronged in some form or fashion whilst they were alive. Most of the spirit follows the soul into judgment, to be sent to Heaven, Hell, or Purgatory."
"There doesn't seem to be a lot of them."
"Most of them do not make it to the surface. They constantly clamber over each other deep inside the magma, hoping for a chance to breathe the air before being hauled back into the molten mass. It is not an ideal existence, but it is just as well that they are not conscious – they are spirits, not souls. Their fury, and their perpetual struggle against other spirits, generate spiritual energy. The pressure and heat of the rock converts this spiritual energy into thermal energy, which in turn feeds the conversion itself. It is an endless cycle of fire and fury."
"A surprisingly scientific endeavor," I commented.
"We are behind your time in terms of technology, but we are not savages. We must make do with what little we have."
"Oh no, I didn't mean it like that," I smiled. "It is very impressive."
"I am glad you think so. I hope you feel more informed on the ways of our world now." Without missing a beat, Suwako Moriya turned and continued down the walkway. "Come. I will show you to the Furnace next."
