Well, a comment in a thread about dream Grimm from u/IamMenace on Reddit lead me to this. Full credit goes to him for the idea, I just made it into a thing. I hope you enjoy.

As she sat in front of the box, scratching her chin in contemplation as she examined the container, Ruby thought long and hard about just what was so odd about the sight in front of her. There was nothing truly perplexing about the box, really. It looked a classic pirate's treasure chest; a wooden box, ordained with a golden lock, with a silver key resting on top of the oak container. Nor was its location baffling, either. The group had stumbled across a ruined house on their travels through the Anima countryside, and went in to investigate on the basis that someone would need help. Rather than anyone injured or dead inside, or even any Grimm ready to be slain, this box rested on the living room rug. And so, it lead to the moment presently occupying their time. Ruby continued to examine the chest, her hands brushing across the oak wood as she looked around, while the other three members of Team RNJR looked at her, waiting for something to happen. "So," the scythe-wielding Huntress off-handedly said, "What do you think's in here?"

"No idea," Jaune simply replied. He, too, was kneeling down, his hands digging through his backpack as he searched for their map, which seemed to have a habit of disappearing on them. "Honestly, if there's a map in there, I'd be really happy."

Peering out the window with a watching eye, Ren didn't turn back as he said "Either that, or a compass. If we could orient ourselves in the right way, it'll still be better than walking blind." His gaze scanned the grass and the rocks, ensuring their safety as they continued to discuss the box.

Sitting down on the couch with her legs crossed and her hands gripping her cheeks in boredom, Nora turned her head to Ruby and sighed. A thought soon crossed her mind, however, which sent her sprawling to her feet. "Or candy!" she suggested, her smile wide as she raised her index finger to the sky.

"Nora," Ren said, "There's no way there's candy in an old box in an abandoned house."

Nora turned to her crush and crossed her arms, frowning as she looked at him. "Firstly, a girl can dream," Nora said, "Second, I'm hungry, and sick of the taste of rations and some of Jaune's instant noodles that he bought months ago! So, unless we have some candy in the pack-"

"Which we don't," Jaune said, confirming it so as he continued to peer through the pack. "Also, I thought you liked those instant noodles-"

"Looking for some in random treasure chests is the best option!" Nora continued, her thoughts ending in a dramatic declaration.

"Nora," Ren gently said, "If you want candy that badly, we can just buy some in the next town."

The energetic girl's first response was to open her mouth in an attempt to protest. After a second, however, she closed it as she thought "Wait, that actually makes sense. Huh. Guess I should have thought about that." Instead, she turned to Ruby and said "Well, in that case, should we just...not open it?"

Ruby deliberated in her head for a second, before reaching out and wrapping her fingers around the key. "I'm sure it's fine. I mean, the place is abandoned, so...what's the worst that can happen?"

"A few things, but I get it," Jaune said, standing up and throwing the straps of his pack back around his shoulders, "Ren's already keeping watch here, so while you're doing that, I'll look out the back."

Ruby nodded, and she slid the silver key into the lock, pushing it in as far as it could go before the keyhole stopped it. She then twisted the key, the soft *click* of the tumblers signalling that the chest was unlocked before she placed both of her hands on the top portion the actual box. She pushed it open, and immediately found two peculiar things about the box. One, both the top and bottom of the opening had holes in them, that looked as though they were drilled in by the long-gone owner. Two, the box was empty. "Wha?" Ruby said, perplexed, "It's...empty?"

Nora held her arms out towards the box as her mouth hung wide. "Really?!" she said, incredulous as she stared at the chest, "All that build-up and there's nothing there?"

"Actually, that is a little strange," Jaune said, only halfway to the back of the house before Ruby opened the chest up. "Why would the owner lock it if there was nothing there?"

"Maybe it was to hold off bandits?" Ruby said, only to look back at the chest. After a second, she said "But then, why leave the key here to begin with?"

It was then that Ren's attention was peaked, and he looked back to his friends as they pondered over the box. As soon as he saw the holes in the box, however, he said "Guys...back away," his voice warning them in a worried tone.

Nora said "What? Why?" right as teeth suddenly slammed through the holes, the force driving the chest closed as the three stepped away. The chest then opened by itself, it's teeth bared and sharp as the bottom of the chest suddenly sprouted a multitude of black tendrils, each one giving off an aura of darkness as the inside was filled with same black mist. Inside the mist, red eyes, like those of a Grimm, emerged, staring directly at Team RNJR. Standing up on it's tendrils, the Mimic clamped it's mouth down before opening itself, giving off the impression of gnashing teeth.

"...So, not candy, then?" Nora summed up, as Ren pulled StormFlower up from his sleeves.

Gripping the green pistols in his hands, Ren yelled "Out of the way!" just as the Mimic raised a tentacle up, Jaune quickly rolling out of the way of a vicious strike as the tendril slammed into the wooden floor. Opening fire, Ren saw that his bullets tore holes in the Mimic's chest, actual wood splintering as he continued fire.

Crescent Rose and Magnhild made a wonderful sound as they activated, Magnhild immediately changing into the hammer form as Nora dashed forward, grinning as she slammed the Mimic's legs in. While it was tripped up, a magnum round tore through its body as Ruby cycled the bolt back, loading another bullet into the chamber. With the beast down, it struggled for a second before Jaune slammed his sword into the creature's abyss, which made it wheeze.

Ruby walked towards the creature and placed the barrel of Crescent Rose inside the beast, as she said "If only you had something." A large bullet suddenly slammed through it, and their first Mimic died. Twirling Crescent Rose around, Ruby then said "Come on! I think I remember where to go; next's town only a mile or two away."

And so, walk out of the building they did, ready for the next step of their journey.

After a few hours, all that was left was the chest, which was currently resting comfortably under a boot, which turned it slightly as the person put his weight on it. Bending down to inspect it further, the man saw a 50. Bullet casing, and picked it up. As soon as his yellow eyes checked every groove with more than a mere glance, Tyrian grinned a sadistic grin. "They were here," he said, dropping the casing, "And if they're heading to Mistral...Then I know where they're going to be…