Once inside the dungeon, Finn and Marshall bother were taken aback by what they saw ahead. The entirety of the cave was encased in what appeared to be diamonds. Everything in the cave was just sparkling from the light that had entered the cave upon their entrance. They were just in awe for a moment.
"Woah... I've never seen this before..." Finn stated as he began to walk forward. The adventurer then pulled a stick from his backpack and lit it using a couple of rocks that he had found on the floor of the cave. Once it was lit, the gentle light radiating off the flames danced and bounced off the walls which made the diamonds sparkle even more. Marshall floated after Finn as his gaze was still on the dazzling gleam of the cave walls around them.
"It's pretty math.. Huh?" Marshall responded but far off into the depths of the cave they both heard a sound. Perhaps it was a rock falling, or a monster, or just a rock that came loose when wind was allowed to enter the long undisturbed cave.
Their attention immediately looked forward and Finn began to walk slower as to make no sounds and he soon made it to a large opening. It had led out to a large room but, this room was even more extravagant than the last. There were sections that led to other pathways, theirs was the one cut from diamond but as Finn glanced around he had noticed that the one closest to theirs was ruby and the one after that was sapphire then emerald and so on. It had taken his breath away for a moment. His thoughts raced, 'How was this cave made?' 'Why are they made of jewels?' and much more. The two boys entered the room further and noticed that maybe five feet ahead, the caved dropped down to lower levels that were laced with a dark onyx. Marshall glided past Finn and examined the part that dropped down and found a ladder that led down.
"Finn,there's a ladder." Marshall stated as he ushered the blonde to the ladder.'
Finn was brought back to earth and nodded as he made his way to where the vampire pointed. He then held the torch with one hand and slowly made his descent down into the unknown with Marshall following after. The two climbed down for about five minutes before they reached the bottom and the cave had switched from a dazzling gleam to a rather ominous feeling. The onyx walls absorbed the light rather than refracted, so, the torch only lit about a five foot radius around them. The two ventured onward and went through a passageway in the lower part of the cave with no idea what lied ahead.
As they kept onward, they kept on but they soon began to hear what sounded like gurgles intertwined with groans, it didn't sound human. At all. Finn slowed down as they entered the opening and as the light slowly entered the darkened room there they were. A large group of radioactive humans? No... Not anymore. The creatures were mainly pinks, yellows, and greens with open eye sockets that were oozing with the radioactive goo that once plagued the Land of Ooo. Finn and Marshall both were in shock and their eyes grew wide at the sight of the horrifying creatures. Once the light shone upon them, the mutants let out a loud groan that echoed through the cave and they all turned their attention to Finn and Marshall in an instant.
"Finn... I think we should go..." Marshall whispered as he placed a hand on the humans shoulder and tried to pull him back but the boy didn't budge.
Finn just stared at the goo oozing creatures and allowed his grass sword to extract from his arm and he took a step forward, swinging the blade enough to cut the creature in half, but even when cut it continued to move and Finn had no idea what to do. So, he and Marshall both ran as fast as they could out of the opening and the mutants soon followed behind. The two made it to the ladder but, so they wouldn't waste time, Marshall wrapped his arms around Finn and puled them both up. When he was pulled, Finn dropped the torch and the creatures stared upward and they soon were smart enough to climb the ladder and Finn's eyes widened.
"Marshall, they're following!" Finn squirmed in the vampires arms as they made it to the jewel encrusted cave part yet again. Marshall sat Finn down and looked over the ladder and sure enough, they were. Finn looked around before grabbing Marshall's hand. Finn then began to pull the vampire back to the diamond part and practically drug him out of the cave. Once to the surface, Finn began to frantically try to shut the cave door to no avail. He stopped and listened closely. The creatures were making their way through the diamond encrusted passage and Finn began to panic.
"Calm down!" Marshall exclaimed before he picked Finn up yet again and started to fly towards the Candy Kingdom. They could at least alert the princess about the oncoming attack from the radioactive mutant creatures. Minutes passed as they made it to the Candy Kingdom and Finn ran as fast as he could to find PB. He ran into her room and just started wailing.
"Princess Bubblegum! Cave! Radioactive things! On the way here! We need to protect the kingdom!" He practically screamed it.
"What!? Those things are on the way here!? We have to prepare for a battle Finn!" She exclaimed and walked swiftly to her window. "Gumball Guardians! Get into your positions!"