The cavern wasn’t natural, of that I was sure. It was another five hundred feet lower than the little pocket I’d claimed earlier, well below the sewer lines running under Derro. If Keeper’s theory was correct, it was part of the ancient machinery used to elevate the city from mundane to a magical paradise.

I doubted it had been like that, but what did I know? The only cities I’d ever seen with a subterranean mysteel infrastructure were ones that flew in the sky, and those weren’t for poor, struggling mages like I’d been. By the time I’d gathered enough power to set foot on such places, I’d already learned enough to realize how they were nothing but foolish, expensive, vanity projects.

I couldn’t even begin to guess what one under a place like Derro had been designed to do, but I reminded myself that this island hadn’t always been a desert. It probably hadn’t even been an island, originally. Breaking apart a whole moon and letting its pieces rain down from the sky had dramatically altered the geography of the world.

Regardless, there was no mysteel in this cavern. Worse, it had partially collapsed. Something had shattered the south wall, leaving me with the options of taking the east exit or trying to dig out half the room. For the time being, I decided it was worth it to send a few scrying spells out to explore while I telekinetically excavated the rubble.

That was a simultaneously easy and complicated task. Moving earth wasn’t hard. Doing it in such a way that even more didn’t come down on my head was a different story. I started with a lot of transmutation spells designed to reinforce the cavern, a somewhat tedious task made slightly easier by the fact that all the stone I was using came directly from the cave-in. By the time I was done, I’d used something like a fifth of the rubble, which still left me with plenty to move.

But now that I didn’t need to worry about being delicate with it, it didn’t take long to clear it out with great, booming applications of force spells. I wasn’t anything approaching subtle, but I was far enough underground that no one up on the surface was going to hear me anyway. And if there was anything living down here, the earlier I found out, the better.

With the way before me open and my divinations returning nothing of interest behind me, I ventured forward. According to Keeper’s best guesses, I should run into something directly west of the Actalus castle, but the problem with underground exploration was that it was incredibly easy to walk right over or under the goal without ever realizing I’d passed it by, separated by a few feet of stone. To help counter that, I started running a spell called earth sense that let me sort of see through the ground around me.

For the most part, it didn’t find anything besides an unusual amount of unmixed stone that I assumed was due to the underground tunnels and caverns being man-made. There were occasional pockets of other material, usually sandstone or sometimes clay, nothing interesting or unexpected. At least, there wasn’t until something in the stone shifted and disappeared from my earth sense.

Frowning, I pumped more mana into the spell to expand the range. Mana started bleeding out of the circuit, too much to be contained in the spell form and cycled back into my core. As soon as that started happening, the shifting spot in the stone flexed and started moving toward me, and a few dozen more came into range.

“Ah,” I said softly. “Unexpected.”

It was a colony of some sort of subterranean monsters, one I thought I recognized. The fact that they were reacting to the excess mana I’d inadvertently dangled as bait when I’d overcharged my spell made it unlikely they were animals, not to mention that they were having no trouble moving through solid stone. It barely even slowed them down.

The closest one angled its approach to breach stone right above my head. I walked forward and watched the gap in my earth sense perception adjust direction. Twenty more all chased me down, coming at me from every possible angle, but none were as close as the first one I’d sensed.

The stone overhead cracked and vanished, probably drawn into the maw of whatever was bearing down on me. Creatures like these always had a few things in common, namely a worm-like body, a mouth that could grind anything that got caught in it into paste, and a thick, nigh-impenetrable hide that made them difficult to injure.

Difficult wasn’t the same as impossible, however. When the monster lunged out of the hole it had chewed through the ceiling, I sent a force lance directly down its gullet. The spell shattered into a hundred smaller shards of force and started spinning around, turning the monster’s guts to slurry as it spasmed in place. Ichor dripped out of a corpse that slid partially out into the air before its body got pinched in the curve of its own tunnel, leaving it hanging in front of me.

I sidestepped the puddle forming at my feet and made it another two steps before the next one dug into the tunnel. It met the same fate, and so did the one after that. At that point, I was forced to stop walking to deal with them as they started popping up three or four at a time.

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I pulled my legs up and levitated, sitting in the air in the center of the tunnel so that I could target the worms coming up beneath my feet. Force lances shot out in every direction, slaughtering the monsters half a dozen at a time. After a minute of that, the worms stopped coming, though I doubted it’d be the last I’d see of them.

I flew forward twenty feet to get clear of the mess before resuming my walk. Never had I been happier that my shield ward could deflect the spatter of those monsters’ churning guts than right now. That alone was worth every scrap of mana it cost me to recharge it back to full capacity.

I made it another ten minutes without incident, not because I didn’t detect more of the monsters in the stone around me, but because I stabilized my extended earth sense spell to stop the mana leakage. Without that to latch onto, it seemed the monsters didn’t notice my passage.

The whole time I was walking, I was being fed information from eight different divinations that were busy mapping out the whole underground complex I’d dug my way into. Whatever else might be here, it was obvious that Keeper had been right about it being artificial. There was far too much worked stone making straight hallways, though they were usually buried under a layer of loose gravel and sand.

Unfortunately, my scrying magic didn’t reveal the prize I was after. The network of tunnels was big, possibly spanning the entire length of the city, though I hadn’t proved that just yet. It was also entirely empty of any trace of mysteel. It was possible it was buried elsewhere and I’d just missed it, or that I hadn’t explored far enough to find it, but Keeper’s theory was that it ran under the entire city, and so far, there was no evidence of that.

Maybe I was just in the wrong section. I’d discovered a few tunnels below or above me, but no connections leading to them. It might be time to make my own. Boring through thirty or forty feet of stone wouldn’t take me all that long, maybe half an hour at the worst, depending on the material. I did a bit of surveying to find a tunnel passing beneath me that wasn’t blocked off by solid stone, then started digging.

That attracted more of the worm monsters, of course. They might ignore me walking around as long as I wasn’t dangling mana in front of them, but there was no way they were going to miss me shaping a magical tunnel when I was deep into their territory. I killed them as they surfaced, hundreds of them this time, and eventually cut my way through the bedrock to the tunnel beneath.

Preceded by a simple light spell, I levitated down into the much narrower tunnel to continue my explorations. Occasionally, one of the burrowing worms would leap out at my light spell, only to pass through it and smack against the opposite wall or floor, where it flopped around until it lined its mouth back up with the stone, then burrowed back into hiding while the light spell flickered slightly at having some of its mana stolen. It was actually harder to kill them that way than it was when they came straight at me, and I quickly gave up bothering to try.

After twenty minutes of exploration, I saw a door through one of my scrying spells. Halting, I examined it while mentally tracing a route from my current location to there. It was metal of some kind, possibly steel, but if so, it had been polished to a high shine. Despite the dust and dirt caking its surface, it was in flawless condition, not a scratch on it. It was lacking any sort of handle, but that was hardly an uncommon characteristic.

I made my way there, noting as I did that the giant worm monsters were getting rarer until finally, they disappeared from my earth sense altogether. By the time I got to the door, it was like they’d never existed at all.

A brief examination was all I needed to get it open. The bolts inside that locked it had to be manipulated by a combination of divination and telekinesis, not because anything was damaged, but because whoever had built the door had designed it that way. Presumably, anybody with a reason to go in or out would have no trouble with that.

Whatever wards might have been placed on the door had long since expired, which made it easy for me to scry past it. After confirming there were no immediate mechanical traps in the area, I pushed the door open, or rather, slid it sideways into a slot in the wall. Beyond was a long, dark hallway made of the same metal.

I tapped my foot against it and cast a few divination spells to identify the composition. As far as I could tell, it was some sort of steel, high quality but otherwise mundane, except it was plated with a different, more brittle, type of metal. It resembled steel, except that it was reflective like polished silver.

What it wasn’t, however, was mysteel. Interesting as it might be, I wasn’t here for this metal. I stepped through the door and started exploring, mostly by sending my scrying spells down the hall, then splitting them up as they came to intersections and forks.

I was starting to despair of finding anything truly valuable when one of my spells stumbled across a room with a large pillar covered in runes. It was hard to tell from just the divination, but I was almost certain. I’d finally found what I was here for. And that much of it… That alone was worth the time and effort I’d spent on this expedition. If there were more pillars scattered around down here, so much the better.

I hurried toward the pillar, following the path my spells had mapped out for me. Within minutes, I was in the room, eyeing up the enormous chunk of mysteel. It was twenty feet tall and eight feet wide, every inch of it carved with runes that no longer had any mana running through them. Perhaps those would give me a clue where to find more.

As I approached the pillar, a hidden panel slid partially open in the wall nearby, revealing some sort of golem. I stepped back, preparing myself to be attacked, but the construct’s eyes just flickered with mana for a moment before it tipped forward and collapsed onto the floor.

“Well… that was anticlimactic,” I said.