(Someone can roll an Arcana check with advantage since you have Katarina in the party :D)

The mimic explodes in a heap of flying wooden splinters and squishy, organic bits as it is struck dead on by Aura's arrow. Combat is over!

Katarina does her best to wipe a bit of the gunk from the monster out of her fur as her rage, and the surge of wild magic, start to simmer down. The vines and flowers tangled around the evil barrel begin to recede back into the earth as the cat calms down. She glances down at her dress and grimaces.

"Perhaps Katarina should stop dressing this way for adventures," she says with a sigh. "In her defense, Katarina thought a diplomatic mission this was to be."

(I think Khessa has the best Intelligence modifier, and it doesn't look like any of us are actually trained in Arcana)

Jasper steps back a few feet, seemingly covered in dripping viscera and chunks of wood? Or bone? Really can’t tell which. Cleaning as much as he can off, I sees that his skin is shining with a vibrant blue color. “What is wrong with my skin? It’s all over me!

The imposing figure of Khessa finds himself covered in wooden splinters and squishy, organic bits, when the mimic, hit in a vital point by an arrow from Aura, explodes; but the blonde arcane warrior doesn't care about that right away. Seeing that the magically grown flowers begin to recede back into the earth as the tabaxi calms down, the tall adventuress scrambles to pluck one by the stem and holds it in her hand, at the moment. The next moment, Khessa is already at Jasper's side: "Are you okay, dear? The dirth on the skin will be washed away, don't worry too much about that, but I saw that horrible thing bit you..." and she tries to examine the wound.

Meanwhile, she turns around for a moment and mentions Katarina and Aura: "Great work girls! I knew that taking you with us would be a great choice!"

And also the tall adventuress hears Echo's bewildered voice from outside, replying: "It's all right my friend! The shapeshifter has just completed his last metamorphosis... into an explosion of debris and guts! Come back, it is safe now! Anyway, you really have to explain to me how you did that thing! That was amazing! Not only did you cast that poison spell, but you also managed to teleport yourself away to a safe place at the same time! Why didn't you ever tell me you knew how to do that? It is astounding!"

Arcana check with advantage since we have Katarina in the party: 12

Khessa realizes that the strange effects of Jasper's skin changing colors and Echo's sudden ability to teleport may be manifestations of wild magic, similar to the wild magical effects that happen when Katarina rages. She notices also that these effects only happened when Jasper and Echo cast a spell. 

"Oh, wait...now that I think about it..." she seems suddenly struck by an idea Khessa "Echo, Jasper...these effects you've experienced so suddenly... the teleportation... the skin that has changed color... those may be manifestations of wild magic, similar to the wild magical effects that happen when Katarina rages! After all, these effects only happened when you cast a spell! If so, the color effect should revert in a while, just like Katarina's flowers, that started to... ungrow, after a while, when her rage subsided".

At that point, the blonde arcane warrior also checks the flower she had picked, the one that had grown under the impulse of the wild magic of the tabaxi barbarian: is the flower still in her hand? Or has it disappeared? If the flower is still in her hand, the tall adventurer tries to smell it, with interest, then places it between two pages of her spellbook, noting what she has just learned about wild magic... Wild or not, it's still magic - so mysterious and intriguing!

Having finished cleaning herself to the best of her abilities and picking the largest chunks of the mimic's body out of her mane, Katarina takes a moment to check how the others are doing.

"Is elf Jasper okay?" the cat asks. "And... where did Echo go to?"

Her concern is quickly abated when she hears Echo calling from just outside the cave and sees that Jasper has only suffered minor injuries. She then turns her attention to the latest manifestation of her wild power.

"A new one that Katarina has not seen before, quite strange... but very pretty," she crouches on all fours to prod and sniff at the ground, not sure herself what happened to the vines and flowers that her anger called into existence.

“I’m quite alright it seems.” Jasper responds to Khessa’s and Katarina’s concerns. “I felt a little pressure and stinging sensation where it bit me but I seem to be fine.” Jasper examines his armor and can see where the teeth sank in and some pitted marks on the chain. “It looks like this could’ve been much more painful.” Jasper sighs slightly and grabs his symbol to the Moon Maiden and prays thanking her for her protection and strength.

Hearing Khessa’s words about the wild magic, Jasper’s a little relieved but also curious. He whispers a few words holding Selune’s symbol. Jasper casts Healing Word on himself. 6

“Woo! We did it!” Aura cheers as she slots Quick’Silver into placed across her back. After making sure that none of her companions are seriously hurt, she takes a moment to pick a few stray splinters from her clothes. While doing so, she listens to the conversation about wild magic, and cannot help but chime in. “Katarina! I’m afraid I do not know much about your wild magic, but it is very impressive. And pretty, too!” Turning too Khessa, she cocks her head inquisitively, lips pursed in thought. “Do you mean that Katarina’s magic is affecting both Echo and Jasper? Or that something else is causing these strange occurrences? Either way, how fascinating!”

Katarina straightens up, having assured herself that her summoned vines have vanished into the dust and she's not going to find them again.

"Many thanks, friend Aura" the feline giggles. "Perhaps friends bring out the best in Katarina? That said... turning elf Jasper blue does not seem like something Katarina's powers would do; she has never seen her magic twist another's in this way... if it could, she would have used it on her stuck-up sorcerer sister!"

As the words leave her mouth, Katarina realizes too late that what she just said about her sister sounded quite vindictive. She looks away, her tail swishing back and forth nervously. It's not hard to tell that the cat is feeling guilty about something.

The tall adventuress frowns for a moment at the tabaxi's words about her sisters: 'What a pity, that she doesn't get along with them!' she thinks 'May I see soon my sisters! And the rest of my family, too…'

But the knowledge that she's just taken another step towards defeating Cryovain wipes out sad thoughts about a situation that she, for now, has no power to change: "Yes," agrees Khessa, approaching Aura to pat her on the back "Really fascinating! In fact, from what Katarina says, it shouldn't be an effect triggered by her... I agree, she would have already noticed it, if she had ever happened to make someone's skin change color! But the there are many similarities between what happened (perhaps spontaneously?) here and what she causes when she unleashes her warlike fury... They are probably both manifestations of Wild Magic, but with different triggers. Maybe the monster's presence was a trigger, here? Anyway, Jasper bravely just cast a new spell..." sighs the blonde arcane warrior, who didn't have time to advise him more caution - for example, move away from the room before trying "let's see if it manifests bizarre effects or not. If they don't manifest, then the monster must have caused them - and now that the monster is no more, all is back to normal. But if they still manifest… perhaps there is a magical perturbation in this room? Maybe a magical machine of the gnomes is responsible of it? Well, let's see...”

(OOC: Does something strange happen as Jasper casts his Healing Word?)

Echo rushes back in within seconds, but the mimic has already been defeated, an arrow stuck in the mess of goo. Seeing the mess stuck on everybody else, she can't help scratching the bad of her head and going: "I'm kind of glad I wasn't there when it fell..." But she doesn't shy away from trying to help Katarina clean her dress. "That was so confusing... and kind of fun? I want to see what happens next!" She blinks curiously at Jasper when he casts his healing word.

As Jasper casts his spell, butterfly wings suddenly sprout from his back! (He now has a flying speed of 30 ft.)

Katarina smiles gratefully as Echo helps her to clean the dress. It seems that, almost as quickly as the guilt and sadness came over the cat, it is gone again and she's back to her normal happy mood.

"Oh... elf Jasper is becoming so pretty!" Katarina says with a laugh as she sees the wings sprout from the elf's back. "But... can he fly with them?"

Khessa admires, in awe, with open mouth, the beautiful new butterfly wings of her beloved elf: "Jasper!" she gasps "They are wonderful! Now you can fly like Tookrashk! You just need a moment to get used to them, I guess... or the magic gave you also the instinct to use them effectively already?" she has her spellbook already in the hands again and starts frantically to report the new marvel, along with notes and speculations "So cute! So it was not the monster, it is the room... or some powerful magical source or machine nearby! How many incredible experiments could be done here... I wonder if it has been the Wild Magic that made that barrel monster grow teeth and come alive..."

“What? Did something happen?” Jasper asks. Out of the corners of his eyes, Jasper sees wings moving. He spins right. Then left. Then right again. He straightens his back and shoulders. The wings begin to flap. Faster and faster. Jasper lifts off the ground.  “Ahhhhh! I’m, I’m flying!” Not noticing, he bumps his head on the low ceilings. “Ouch! Ummm? How do these work?” Jasper tries to push towards the room entrance and just as he leans in, the wings push him forward and out the threshold. 
Pushing through the tunnels to the rope bridge, Jasper stops momentarily. He takes a deep breathe and lifts up and up. Thirty feet! Sixty feet! Jasper looks high into the sky as he flys higher and higher. Soon he’s about 200 feet in the air and he looks all around him. His eyes widen as he looks down. A little vertigo sets in what seems like forever. He close his eyes to calm himself. He smiles and opens his eyes thinking about Khessa. He slowly returns to the bridge. That was a good first try. 

Seeing all the strange things happening, Katarina is going to use an action to expend a use of Magic Awareness to see if she can sniff out what is causing the tides of magic to shift in such a strange fashion whenever her friends cast their spells.

Magic Awareness: As an action, you can open your awareness to the presence of concentrated magic. Until the end of your next turn, you know the location of any spell or magic item within 60 ft. of you that isn’t behind total cover. When you sense a spell, you learn which school of magic it belongs to.

Khessa apprehensively watches her beloved elf take flight... 'He was afraid of height on the bridge... He won't panic, flying, I hope? Maybe, on the contrary, the wings will make him feel more confident...'

Seeing hom finally succeed in actually hovering, the blonde arcane warrior looks at him with admiration: his elven elegance matches so well those graceful butterfly wings...

When he lands again, the tall adventuress runs up to him, hugs him and kisses him on the cheek: "Jasper! You're amazing! Flying on these wings, you look like the heavenly angel that you are!"

Then she turns to everyone: "Shall we go and announce our success to the gnomes?"

Quote from Mister_Whisker >>

Magic Awareness: As an action, you can open your awareness to the presence of concentrated magic. Until the end of your next turn, you know the location of any spell or magic item within 60 ft. of you that isn’t behind total cover. When you sense a spell, you learn which school of magic it belongs to.

You sense that Gnomengarde itself is a source of wild magic and suspect that using magic in Gnomengarde often has unpredictable wild magic effects.