A/N: So I forget that life still happens whether I want to write or not, so I'll try for every day but as the lateness of this update shows, I may not always succeed. Hope everyone's still enjoying/following, as this is a hell of a lot of fun to write. Write a review if you liked/didn't like it, I'm always looking to improve :)

Fionna began making her way carefully down the stairs, keeping a hand against the cold stone to her side. Between the night outside and darkness inside she couldn't make out if the stairs beneath her were in good state or not, and proceeded on them gingerly. Finn followed right behind her, taking equal caution as he squinted into the dim light at the base of the stairwell. The stairs descended sharply, taking the pair deep into the ground as they picked their way down. As they approached the base, Fionna looked back up towards the entrance, seeing nothing but the distant twinkle of a few stars. The pair reached the base of the stairway and went side-by-side into the next chamber, both of their jaws dropping when they entered. The dim lighting was being provided by a vast network of coloured crystal protruding at all angles from the stony walls of the tunnel. Each crystal was softly pulsating with a dim light, creating a field of changing colours that washed over the room. The duo approached a cluster of gems nearby, momentarily transfixed by the shimmering ocean of light they were witnessing. Fionna leaned close, peering into the crystals to try and find the source of the light. She saw nothing but a distorted reflection of the stone it rested on; the light was some form of magical property. Finn meanwhile had run his hand down several, fascinated by the subtle thrum he felt in his fingers as they passed over the gems.

"Hey Fionna, touch one of them, they feel like they're alive."

Fionna tried herself, delighted at the feeling in her palm as she pressed it down on an emerald green crystal. As her hand ran down it, the crystal's light began to grow brighter, shining more strongly against those of its brothers nearby

"It feels like Cake's belly when she's purring," she remarked, "I wonder what makes them do that?"

"I have no idea, but it's really cool." Finn replied emphatically. He wandered down the chamber's wall, tapping various crystals as he went. At his touch, each one shone a little brighter, and the pair noticed that a quiet hum had also begun to build in the room. Fionna looked around, both fascinated and suspicious with the sudden, building noise.

"Finn, maybe we shouldn't play around with these. Who knows what they do?" She looked at Finn with concern.

He stopped just short of tapping another, considering her words. He knew she was probably right, so he mustered up some willpower and resisted the urge to tap one more before leaving the area. He turned, giving Fionna an exaggerated slump of his shoulders.

"Oh fiiiiiine," he pretended to pout, before straightening up and heading further down the tunnel. Fionna dawdled a moment, looking at the twinkling lights a moment longer, before reaching her finger out and tapping the crystal she'd stopped Finn from touching. The brilliant azure gem light up and added its own small hum to the low drone. Fionna smiled.

When we leave here, we're totally taking some of these with us.

She skipped a few feet down the tunnel, catching up with Finn and taking his side as they continued onwards. Behind her, the crystals on the walls started to pulse with light as the humming sound began reverberating around the tunnel walls. Slowly but surely more crystals lit up, and the humming sound began to grow in intensity. Finn and Fionna made their way down the tunnel oblivious to the creeping wall of growing light and sound slowly following their path.

The adventurers continued moving through the tunnel, both smiling at the gorgeous crystals lighting their path as they went. The tunnel they walked in contained many twists and turns, but they noticed that it was also slowly tapering down as they proceeded. Soon the amicable space between the pair shortened, as the walls forced them closer together if they wanted to walk beside one another. Neither of them commented on it, both feeling a little awkward when their arms began rubbing together as they continued on. Fionna noticed how unnaturally warm Finn's skin felt compared to the admittedly cold cavern they walked; in fact it occurred to her that it had actually been getting colder as they went further. Finn hadn't really noticed the temperature, as he was focusing very hard on finding something to talk to Fionna about. He was usually fine adventuring in silence with Jake, but he felt compelled to get Fionna talking again, if only to hear her laugh again.

"Uhm, hey Fionna?" he began, thinking of something to ask her, "Jake's got kids with his girlfriend, and you said Cake was with a rainicorn too, do they have kids?"

"Yeah, Cake's been taking care of them for close to a year now." she replied easily, "You should have seen her while she was pregnant. She couldn't do a whole lot, especially stretching her body, so I did a bunch of adventures solo."

"Wow," Finn said, impressed, "I can only think of a few things I've done without Jake, how'd you manage?"

"Using this." Fionna smirked and tapped her head, "I realized how used I'd gotten to just having Cake do the tricky stuff so I had to learn to get through dungeons the hard way. It wasn't easy though, to be honest I miss having her around for it." A thought occurred to her then, "Hey wait, why isn't Jake helping raise the kids? Lord Monochromicorn comes over all the time to help out. Their kids grow fast, I guess rainicorns are like that, but they're still just little tykes."

"Huh, I guess it must have to do with the gender thing. Jake's gf Lady was the one with the kids, and they grew really fast. They're practically older than he is now. Wonder if Lady being the mother had something to do with it."

The pair mulled over yet another weird difference in their worlds before they abruptly squished into each other. Their walking space had dwindled enough that they both couldn't fit in the tunnel walking beside one another without also scraping along the crystals. Finn took a half step back and bowed dramatically, raising his hands to signal her to pass him. She giggled and did so, walking another few feet until the snaking tunnel led straight out to an opening. She hurried herself along, feeling slightly constricted by how small the tunnel had gotten. She slipped through the smaller archway of dirt and stone and entered a more spacious chamber. Finn followed suit, but momentarily yelped in surprise as his larger frame caused his arm to get scratched by a crystal as he passed through the same passage. He eyed his arm, seeing a small nick but not much else. The crystal his arm had touched lit up, this one a soft lavender. He shrugged, joining Fionna as they gazed at the new area.

The chamber they had entered was a large maze-like catacomb, filled with rows and rows of skeletons holding a wealth of different tools and weapons. The space was sparsely lit by some sconces placed throughout, all lit with a sickly green fire. The pair stood on a raised platform, looking down over the tomb below, which expanded outwards for several hundred feet of twisting hallways. Finn looked around them and pointed out a winding stairway leading down into the maze, but Fionna stopped him from going over to them.

"Finn look," she said, pointing into the distance, "I think that's what they're keeping here."

At the back of the open chamber Finn could see a faint red glow of some object or other, which stood on a dais raised beneath a mammoth pile of bones. Neither of them could determine what the item was from their vantage point, but they both felt excitement at the possibilities. They took the stairway down, reaching the flattened base where a few of the same green torches rested on the wall. Both adventurers reached up and grabbed themselves one, proceeding onward bathed the eerie light they provided. The catacomb walls were far higher from their position on the ground than they had appeared from up high, easily reaching twenty feet. The sides of the catacomb walls were hollowed out, to make room for the legions of skeletons that were posed inside. Finn and Fionna approached them warily, looking at a collection of bony bodies that were dressed and equipped as farmers. They wore straw hats on their skulls, and had pitchforks, hoes, and shovels grasped in their ivory digits. Fionna drew her sword out of habit, holding it close to her side as Finn approached one of the bodies. He reached out a hand pushed its shoulder, jumping back with his fists up in case it came to life. He was slightly disappointed when the skeleton just shifted back from the push, leaning against the wall of the socket it was placed in. A quick examination and some thrown rocks later, the pair concluded that none of the skeletons around them were waiting in ambush, and they slowly made their way into the maze. They proceeded about ten feet before they were faced with a simple fork in the path.

"We should leave a marking or something so we know where we came from." Fionna suggested.

Finn nodded, and walked over to a skeleton placed nearby. This one had a leather helmet on, but the gear was comically oversized for its skull. Finn bopped it on the helm, the force sending the bones rattling to the ground as the skeleton collapsed. He then pulled out a few bones, which popped apart easily, and laid a simple bone arrow on the ground at the fork, pointing out towards the exit. He smiled at his handiwork and turned to Fionna.

"That work?"

"Yeah, good thinking Finn. Now we've just got to find out way through here."

The pair began a slow and methodical trip through the maze, facing more than a few dead ends along the way. Fionna remained on her guard the entire time, sword and torch in hand to smite any skeleton that turned out to be alive. She kept her eyes peeled for any sign of traps as well, as a feeling in her gut told her things were going entirely too well so far. Finn took a far more relaxed approach, taking time now and again to examine the newest outfits and equipment that the skeletons around them were toting. He was noticing a pattern as the skeletons went from more work and tool based to fighters, to proper soldiers with ranks and armour. He couldn't help but admire some of the ornate seeming weapons that some of them carried as well, but he had no interest in trading his family sword for any stuffy old substitute. Fionna couldn't help but watch him as he puttered about, poking and prodding at the skeletons, imitating their poses, and generally making a mess as he knocked one apart every intersection to mark where they'd come from. She felt a small twinge of regret as she thought about her own dungeoneering and how she'd been forced to take everything more seriously without Cake by her side all the time. She forced herself to take a deep breath and tried to relax a bit, sheathing her sword in her pack. She wasn't alone this time, she could afford to let herself have more fun without having to worry as much. Finn certainly didn't seem worried, as he struck a particularly macho pose beside a skeleton doing the same. He turned his head and caught her staring at him and suddenly felt very self conscious, rubbing his arm sheepishly and blushing. Fionna realized she'd been staring and also felt embarrassed, stammering to try and find something to say to cover it up. Finn's attention had been hooked elsewhere however, as he saw a red glow at the end of one of the long hallways at the intersection they were at.

"Hey Fionna look! That glow! It's the thing we're looking for!"

Fionna barely had time to look before she felt Finn grab her hand and they took off at an excited sprint to get to it. They reached the end of the hall and turned, both stopping dead in their tracks. The source of the glow was certainly in front of them, but the bonepile it rested upon was gargantuan.

"Well," Fionna breathed out, "that could be a problem."

Finn rubbed his chin pensively, examining the pile. It was at least a hundred feet up, lacked any stairs or obvious routes up, and looked both unsteady and hazardous. The chance to fall seemed immense, and especially without Jake there to either reach up or catch him, he didn't relish the thought of climbing it. He had a moment of appreciation for how hard Fionna must have had it, not having Cake there all the time anymore, if nothing else Finn saw just how convenient it was to have a magical dog as his best friend. He turned to see Fionna stroking one of the ears of her hat, evidentially thinking about the problem as well.

"Think we could bring it down?" Finn asked.

"No, we'd get buried if we tried. And I don't know about you but I'm not climbing that."

Finn shook his head. He didn't have a fear of heights, and knew he was a good climber, but unlike a tree, this pile seemed ready to fall apart. Fionna snapped her fingers behind him.

"Maybe this is a trick. Let's see if there's a button somewhere that make stairs or something!" she suggested.

The pair moved to the base of the pile, separating to find some switch or lever to show them the answer. Their search was very quickly interrupted by a rumbling from the pile. They both sprinted back to the catacombs, ready to flee if the pile started coming down on them. To their surprise however, the pile started to gather itself together instead of falling apart. The various bones started to shift and align, forming what looked like a giant humanoid figure. Arms spread out and large bone-locked hands formed, as did two large legs. The red glow continued, but the bones formed around it and created a large skull, eye sockets being lit by the now sinister seeming red light. Now fully formed, the bone golem stretched its arms into the air and let out a mighty yawn that shook dust from the catacomb shelves.

Finn and Fionna stood with eyes wide as the creature folded itself over to stand hunched, with its large arms acting as supports. Neither of them actively noticed that they were grasping one another's hands. Though devoid of eyes, they could feel the golem's gaze fall over them, as it leaned its head forward. The creature's makeshift jaw creaked open, and a booming voice echoed from it.

"Who dares to enter our tomb?"

Post A/N: Suspenseful ending! I know the AT wiki calls Monochromicorns their own race but that's such a minute detail I elected to ignore it.