Three weeks shy of Saskia’s third birthday, in the midst of a record-breaking heatwave, her mother almost killed her.

Alice Wendle strapped her daughter into the back seat of her not-so-snazzy new Toyota Corolla, drove to work, and parked in the company car park, before locking the vehicle and hurrying into the office, five minutes late for a meeting. This was little different from any other work day, but for one thing. This day her stress-addled, sleep-deprived brain forgot the crucial step of dropping her daughter off at daycare.

Saskia was only semi-conscious by the time a passer-by came to her rescue and broke her out of the vehicle. The paramedics who checked her over afterward and rushed her to hospital said she’d been just minutes away from death.

Years later, when Alice confessed to her daughter about the incident, she came as close to breaking down as Saskia had ever seen her. She’d never forgiven herself for that near-infanticidal lapse of memory.

As for Saskia herself, she didn’t remember much. Into her early teenage years she’d had these brief moments, now and then, when she felt a rising panic; a feeling of being trapped; of suffocating. As the years passed, so too had those terrifying moments, until all that remained were memories of memories. It had been a long time since she’d relived the experience directly.

Until now. Now she was pretty sure the inside of the car had felt a lot like it did here in Wilbergond.

The heat of this place was enough to make her want to curl up and die. There was no escaping it; no shady patch in which to find shelter. The humidity level was so far off the metaphorical charts that had they existed, the charts would’ve wilted into a soggy mess and dissolved. An hour of sweltering in this jungle sauna had slowed their pace to a crawl, and Saskia could have sworn her eyeballs were slowly simmering in her skull.

Mopping her grimy, sweat-streaked brow with the back of her hand, she scowled at her friend. “That one time, I may have said I’d follow you into hell, Ruhildi, but I didn’t mean it literally.”

This was a pretty kind of hell, she had to admit; full of bizarre and colourful sights. Some of those sights had teeth and claws and chittering mandibles. The owners of said appendages didn’t seem particularly intimidated by the big scary one-armed troll, the tiny, but arguably scarier dwarven necromancer, or their elven captive, who may be bound and helpless, but whose dour expression was enough to give any would-be predators a case of the gloomies. Saskia had been forced to get stompy on more than one occasion, and had earned an assortment of bites and cuts on her feet and ankles for her trouble.

The denizens of Wilbergond were a tenacious lot. Even the herbivores were bristling with natural defences. Scaly hides and tough carapaces abounded, along with an impressive array of horns and antlers.

Small wonder, in a place as brutal and unforgiving as this. Distant screeches and growls and slurping sounds assaulted her ears, warning her about the denizens she hadn’t yet met: the apex predators of this primal howlscape. Even more ominous were the carnelian-red markers roaming the periphery of her minimap.

Red means dead, she reminded herself for the umpteenth time.

“We surface creatures were never meant to tread in such a place as this,” said Garrain, wincing as he lifted his scalded foot out of a burbling pool.

“For once I agree with him,” said Saskia. “I really hope we can find the passage out of here soon. I don’t wanna boil alive. Or get eaten.”

“Would that ’twere so easy to find,” said Ruhildi. “Alas, I’ve not set foot in Wilbergond afore. All I ken is what the stories told of this Hollow. They made no mention of the arlium flow.” She cast her gaze up at the column of fiery white liquid inexplicably rising up to the ceiling. “But they did speak of a passage to Dwallondorn. If we make it that far—”

“Oh now you’re just overflowing with confidence,” interjected Saskai.

“If we should perish, I’ll take solace in the fact that your sadistic disciple dies with me, demon,” said Garrain.

“She’s not my—ugh,” groaned Saskia. “Okay Ruhildi, there’s no way we’re gonna die down here now. We’re not giving him the satisfaction.”

Ruhildi’s lips curled up ever so slightly. “In that, we’re of one mind, Sashki. As I were saying afore you interrupted: from Dwallondorn, we can take the prime passage the rest of the way down to the ’Neath. ’Tis a well-tread path; one I myself have taken afore.”

“Okay, now you’re talking. I just hope Dwallondorn isn’t as stifling as this.” Saskia glanced up at the source of the heat. “So that’s arlium? Shoulda known it wasn’t plain old magma. Magma doesn’t defy gravity.”

“I don’t ken what you mean by magma,” said Ruhildi. “Molten arlium is the lifeblood of Arbor Mundi.”

“Just so we’re clear, this is the same stuff you use for your magic?” asked Saskia.

“The very same. Only here it burns hotter than the hottest dwarrow furnace.”

“So…why is it rising?”

“’Tis just what arlium does when it gets hot enough. When it nears the surface, it starts to cool, and sinks back down to the main artery, where it heats up anew. Just as our hearts push blood through our bodies, so too does the lifeblood of Arbor Mundi flow.”

“Huh. Interesting.” So when heated, arlium started to defy gravity, or at least became lighter than air. Just a bit cooler (but still hot enough to remain liquid, presumably) and it lost this property. On Earth, there were gasses lighter than air, but no liquids, and certainly nothing that changed so dramatically while remaining liquid. So…magic?

Yup, she decided. Definitely magic.

“Alas, methinks the passage to Dwallondorn lies on the other side of the arlium flow,” said Ruhildi. “We’ve a ways to go yet, and it’ll get worse afore it gets better.”

“I can hardly wait,” sighed Saskia. “But I thought you said you’ve never been here before and didn’t know where the passage was?”

“I don’t ken precisely where to find it. But I ken which direction to go. I told you about the stone sense already, Sashki.”

“Yeah, but isn’t that a really close-range thing?”

“To feel details, aye, fair close,” said Ruhildi. “But the stone sense also gives me a flawless sense of direction. I’m taking us in the direction we’re like to find Dwallondorn, even though I ken not the exact route.”

“Oh, I suppose that makes sense.” It seemed Saskia wasn’t the only one with a compass in her head. “Dwallondorn is to the north then; toward the trunk of the world tree.”

“Aye, near the shore of the Arnean Sea.”

Saskia thought about that for a moment, before asking, “So why isn’t it underwater then? Why aren’t all of these caves completely flooded?”

“That’s a fair good question, Sashki. An arborologist once told me the arlium arteries and veins breathe the air—or mayhap make new air. I forget.”

Considering her words, Saskia came to the conclusion that maybe they weren’t complete bunk. Her rudimentary knowledge of biology told her that plants did indeed breathe, though oxygen came out of them instead of going in. The air did feel really thick down here, and there was an awful lot more life than she’d expected to find so deep underground. It might explain why the air grew thin and cold high up in the mountains, as it did on Earth, but not in places where this branch of the world tree curled up into spurs taller than any normal peak. If those spurs had arlium flowing closer to the surface, drawing the air close, or maybe even replenishing the atmosphere…

Again she heard that dogawful throat-clearing noise. She prayed they’d never meet whatever it was that made that sound, but a part of her was also curious…

As they drew closer to the column of fire, the jungle gave way to parched earth and blackened stone. It wasn’t by choice that they came this close to the most inhospitable part of Wilbergond, but an unfortunate consequence of its geography. The cavern was shaped like an hourglass, with the inferno raging at the choke point in the middle. The best they could do was scramble down into a trench at the cavern’s edge whose high walls shielded them from the worst of the radiated heat.

Incredibly, there were things that grew even here: great fungal fans on brittle stems like tree trunks, and long, tubular things with bulging tips.

“Aye, they do look like a certain something,” said Ruhildi, following Saskia’s gaze.

“Yeah, they look like…skinny purple mushrooms,” said Saskia.

“Och, so that’s what your people call them. You ken, there’s sure to be arlithite in those stems, if you were to chew on one…”

“Get your mind out of the gutter, Ruhildi.”

“I ken not what you mean,” said the dwarf, her face the picture of innocence. “My mind is just fine where it is.”

So yeah, the heat was making them a bit loopy. That’s my excuse and I’m sticking to it, she thought to herself.

As they dashed through the trench, there was one brief, horrifying instant when her head rose above the walls and she gazed directly into the heart of the inferno. In that instant, she could make out what looked like flaming birds flitting about next to the surface of the molten arlium.

“Were those…phoenixes?” she wondered aloud after she’d doused her smouldering hair.

“Methinks those were scorchwings you saw,” said Ruhildi upon hearing Saskia’s description. “We’ve naught to fear from such beasts. The fire sustains them. Were they to come down here where it’s cooler, they’d petrify fair quick.”

“Huh,” said Saskia. Nothing like their mythological lookalikes then.

Several minutes later, Ruhildi drew to an abrupt halt. Ahead of them in the trench, perched on a mound of dirt and stone were a pair of wide, bulbous forms the colour of charcoal; with leathery hides bristling with thick spiky protuberances, and thick tails tipped with spiked clubs. Then she caught sight of their eyes; black and multifaceted and…ugh…far too numerous. She counted seven on each head.

“Threshers,” said Ruhildi

“Yay,” said Saskia. “Name like that, they must be all cuddles.”

“You wouldn’t want to be cuddling up to a thresher, Sashki.”

“One day, I’m gonna have to teach you about a thing called sarcasm. Think we can get past them without a fight?”

“Och no,” said Ruhildi. “Threshers don’t eat meat, but they’re like to squash anyone who comes near their nest.”

“And their nest is…right in our path,” finished Saskia, seeing the debris piled beneath the two beasts. “There’s no way around. Fan-frocking-tabulous.”

“There may be another option,” said Garrain.

Both of them turned to him.

“Return my staff to me, and I’ll cast a spell to pacify—”

“No,” said both Saskia and Ruhildi in unison.

He let out a ragged sigh. “It was worth an attempt. Very well. Slaughter away then.”

There came a sound halfway between a snuffle and a growl, followed by an answering roar. One of the monsters slid down from the nest. The beast scuffled forward on stubby legs, beating its tail club rhythmically against the ground as it moved. Probably trying to scare the invaders off, but unfortunately for everyone concerned, there was nowhere for the invaders to go but through.

“They’ve spotted us,” said Saskia.

“Aye,” said Ruhildi. “I can see. I have eyes and ears too, you ken.”

“Oh good. Keep them on our prisoner, will you, while I hold back this monster.” Hurriedly, Saskia unwound Garrain’s rope from her waist and tied it to the thick trunk of a fungal spire.

For a moment, she considered taking the elf’s glaive into battle, before discarding the idea. It was an impressive weapon—probably far more deadly than Mjölnir—but having never practised with such weapons, she’d be more of a danger to herself than her opponents. Also, to survive in an environment like this, these creatures must be seriously resistant to heat, so the singeing edge of that blade would more than likely be wasted on them.

Mjölnir it was then. She bared her teeth at the threshers, hefting the massive hammer in her one good hand. “Time to get my troll on!”

“If the beast should get past you, I won’t be of any use, tied up like this,” said Garrain.

“Yeah,” said Saskia. “Your point?”

“I can help!” he insisted. “If not with magic, then with skill at arms!”

“Maybe, but we can’t take that chance right now, so just…try not to die.” Without sparing him another glance, she advanced on the approaching thresher.

Only as it drew near did she begin to get a sense of just how big this creature was. The word elephant sprang to mind, though it looked nothing like an elephant. There were very few beasts that could truly threaten a troll, but this thing…well, it’d give her a run for her money.

Closing the remaining distance, Saskia lunged forward, bringing Mjölnir down upon a vulnerable-looking cluster of eyes that regarded her unblinkingly. Or that was her intent. Her movement felt sluggish, weighed down by the oppressive heat. The hammer thudded into brittle earth, sending a cloud of dust into the air.

It took her a long moment to register what went wrong. Very nearly a moment too late. The beast had spun about, and its vicious club of a tail was sweeping toward her like a wrecking ball covered in nails.

Leaping upward in the nick of time, she felt a gust of displaced air press against her feet. She landed awkwardly and almost fell onto her butt.

Recovering quickly, she lashed out at the thresher’s flank. This time, her blow struck home, cracking one of its spines. The beast emitted a short, sharp yip, bringing to mind the sound her dog Cerberus had made when she slammed the door on his tail.

Dogramit! Why’d she have to think of that? Now she was actually feeling sorry for the bug-eyed monster that was trying to kill her!

Speaking of which, its tail was hurtling back toward her; this time high in the air. Too high to jump. With no time for thought, she dropped low to the ground.

There was a horrible grinding sound as it scraped across her armoured back. With a loud thud, the spiked club at the end of the tail smashed into the wall of the trench.

Saskia staggered to her feet. That had been too close. The fact that she hadn’t been lifted up and embedded in the wall meant it must have barely touched her. Probably. She couldn’t spare a moment to check the damage.

Then she saw what had happened, and almost burst out laughing.

The beast’s clubbed tail was stuck in the wall.

Well okay, it wasn’t that funny. But it was really convenient for her. Seizing the opportunity, she began to wail on the fail-tail, hammering its spikes deeper and deeper into the rock wall. The thresher growled and twitched as it tried to wrench its tail free, to no avail.

Carefully avoiding its heaving bulk, she circled around to where its vulnerable eyes and snout lay. She brought the hammer down. This time the beast didn’t turn its head away fast enough. There was a cringe-inducing splat, and a spray of what she could only assume were…oh god those were eyeball juices running down her legs.

Two quick blows, and the beast stopped twitching. She backed away, feeling a little sick to the stomach.

The creature stirred. Saskia let out a yell of surprise, raising Mjölnir.

“Stop, Sashki!” called out Ruhildi. “The thresher’s mine. ’Tis on our side now.”

Sure enough, as the beast lurched onto its feet, it made no move to attack her. Ruhildi had just raised its corpse to fight for them.

It took some work to lever the beast’s tail spikes out of the wall. Then she turned and watched grimly as Ruhildi’s minion lumbered off to deal with the remaining thresher, who had remained behind to guard the nest.

This is so wrong, thought Saskia, listening to the frantic squeals and growls that emerged from atop the nest as the dead thresher clubbed its mate to death.

Scrambling over the ruins of the nest, Saskia winced as she spotted the crushed forms of several miniature threshers scattered among the mess of dried mud and stones.

“We killed their young,” said Saskia, swallowing the lump in her throat.

“’Twere them or us,” said Ruhildi. “’Twere a mercy, methinks. They wouldn’t have survived long without their parents.”

Nothing else stood in their way as they made their way through the remainder of the trench. The pair of enormous undead monsters charging ahead of them probably had something to do with that.

When at last they entered the festering fungal jungle on the other side, Saskia let out a sigh of relief, despite the fact that it was still a squillion degrees, her feet were blistering, and the rest of her exposed skin had turned a very un-troll-like shade of red. Ruhildi and Garrain looked just as crispy. Hopefully it would get better from here though, as they put more distance between themselves and the column of fire.

Her relief was short-lived. Pressing further into the jungle, they came across a long clearing where the trees and fungal spires had fallen, and the undergrowth had been pressed flat, as if a giant steamroller had driven over it.

“We’d best move quickly,” said Ruhildi.

“What? Why?” Saskia looked sharply at her friend, who was eyeing the flattened fungus and toppled trees with an edge of tension lining her face. This was about as nervous a look as she’d ever seen on the dwarf.

Silently, Ruhildi stepped out into the clearing, gesturing for them to follow.

As they neared the treeline to the north, there came that dreadful hoicking sound again. At the same moment, a gigantic violet marker appeared on the western edge of her minimap. It was behind a hill far beyond the treeline, so she still couldn’t see the source of that horrible sound with her naked eye. If they were really lucky, they wouldn’t get to see it. She’d only ever encountered one violet marker before, and that had been…

There was a distant crackling rumble, like the beginnings of an avalanche. Or the toppling of many trees.

The violet marker turned and began to slide in their direction.

“Guys,” she said. “We’ve gotta run! Something really bloody big is coming this way!”

Garrain held up his bound wrists. “Untie me, demon, lest I slow you down.”

“I have a better idea,” said Saskia. She slung him over her shoulder, ignoring his grunt of indignation. As they raced toward the edge of the clearing, she warned him, “Reach for the staff, and I’ll break your arms.” So much for being the good cop, she thought.

Ruhildi kept glancing back at the enormous stubby-legged beasts lumbering after them. “My minions can’t keep up,” she said.

Saskia sighed. The threshers were like tanks; heavily armoured but not especially quick over long distances. “How long can you maintain control of them? Maybe we could use them as a distraction?”

“Until we enter the treeline on the other side of the clearing,” said Ruhildi. “Once I can no longer see them, the spell will be broken and they’ll revert to ordinary corpses.”

“Oh well, can’t be helped,” said Saskia. “They probably wouldn’t last long against whatever it is that’s coming.”

They re-entered the cover of the jungle and raced toward the cavern’s northern edge, until Saskia spotted a tunnel on her minimap.

“This way!” she shouted.

The creature continued on its eastward path rather than veering north after them. It was close though; too close. Trees and fungal toward swayed around them, buffeted by its passing. She prayed the monster wouldn’t catch the delicious scent of their crispy, well-cooked flesh.

They passed through a narrow ravine between two hills. On the other side, the passage out beckoned.

It was hard to miss. A jumbo jet could’ve fitted through that opening. The mouth of the tunnel was a barren, desolate wasteland, stripped of all vegetation, aside from a few tiny fungal growths poking up between the rocks. They’d find no cover here. There was nothing to do but run for it, and pray that they didn’t get spotted by…whatever it was.

The final dash for safety seemed to last an eternity. Saskia’s gaze kept flicking back and forth between her minimap and the receding jungle. The creature was now heading southeast, directly away from them. As long as it didn’t turn around, they’d be home free.

It didn’t turn around.

Scrambling up the steep slope out of the cavern, she spared one final backward glance. There came that terrible sound again, and from behind the hill, a writhing forest of somethings licked up high into the air, snatching at a swarm of screeching bats.

And then they were clear.

The tunnel resembled the one through which they’d entered Wilbergond, but there was just small stream running down it, and the only things that grew in here were tiny phosphorescent plants peeking up from between the rocks.

Slowly, the temperature began to ease, until at last she felt like she could breathe again. Pulling in great droughts of cool air, Saskia splashed water over her face, sighing in relief. Garrain took it a step further, falling backward into the water, where he lay immersed up to his chin.

“I so wish I could do that,” she said, eyeing him enviously. She was far too big to take a proper dunk in this shallow stream. “That place was the worst.”

“We have to go back,” said Ruhildi, glancing down at a large puddle of slime that had collected in a cavity beside the stream. The nearby walls were splashed with the same stuff.

“Seriously?” said Saskia. “We finally make it to safety and you want us to crawl back into the cook pot? We’ve been going for a day and a half straight. We need sleep.”

“Not here,” insisted her friend. “If we try to sleep here, we’ll find no rest ’cept the final one.”

“What do you mean by that? Just—oh, hold on.” Saskia eyed her minimap. “There’s something up ahead. A lot of somethings.”

On her map, she could see that the tunnel opened out into a wider chamber with a lake at its centre. Nothing as impressive as Wilbergond, but still large enough to contain a city block with room to spare. In and around the lake were a multitude of orange markers. One or two orange dots wouldn’t be too much of a concern, but this many could pose a serious threat.

“As I were saying,” said Ruhildi. “’Twould be best if we find another passage out.”

“Okay so here’s an idea,” said Saskia. “Let’s find another way out.” Then she let out a rather embarrassing squawk of fright. “Um…on second thought, let’s keep going.”

A huge violet marker had appeared at the mouth of the tunnel. The ground shuddered slightly beneath her feet, accompanied by the sound of something very large squeezing into a tight space.

For the second time today, they found themselves running for their lives.

Emerging into the large chamber she’d seen on her map—a chamber which, too late, she saw to be a dead end—she took in the sight of the lake below, seething with scores of long sinuous bodies that darted too and fro like giant tadpoles. Many more lay around the shore; some of them feeding, while others were the food. At first glance, she’d mistaken the creatures for cave crawlers, but one look at their feeding habits dispelled that notion. Cave crawlers were fungivores, and they also had legs. These critters were closer to worms than centipedes.

“Deepworm spawning grounds,” whispered Ruhildi. “Tread carefully. We need to find a place to hide in here.”

Deepworm. The word sent a shiver down Saskia’s spine as she recalled the colossal monster she’d found trapped in the ice of a cave high in the mountains above.

As for where they could hide, well it wasn’t looking good. There were numerous tiny cracks and crevices through which water and cool air flowed, but most were far too narrow to be of use to them. According to her minimap, the best of the bad options available was…

“Up there.” Saskia pointed to a little nook halfway up the cavern wall on the far side of the lake. It’d be a tight squeeze for her.

The three of them crept silently around the edge of the chamber. If they were really quiet and really lucky, they might be able to get past without attracting unwanted attention.

Halfway around the lake, their luck ran out.

One of the cannibalistic worms reared up and turned an eyeless head toward them, revealing a rubbery, circular mouth, toothless and oozing with a putrid substance that sizzled and smoked when it dripped onto the corpse upon which it fed. The horror show let out a gurgling, cooing sound, almost like a human baby. A dozen more oozing maws lifted from their meals, turning their attention to the new arrivals.

The rushing, rumbling sound behind them reached a crescendo. Saskia whirled about in time to see their doom burst into the cavern behind them, smashing aside boulders as if they were tiny pebbles: a vast tubular creature almost as wide as the opening it flowed through.

Saskia gulped. “So that’s the mama worm.”