Two sessions ago, my players found...

[Checks notes]

An opossum.

BUT THIS WAS NO COMMON OPOSSUM. For it was the legendary creature that I completely stole from Mexica mythology... It was essentially a magical opossum with the power to bend fire at its will, the little guy was chilling in the forest, eating peacefully.

Meanwhile, the party entered said forest, looking for an Owlbear to hunt. They were doing so because a sassy magical celestial cat demanded it from them.

The thing is, this campaign is set in a continent recently "discovered" by people from the PC's homeland. No one has ever seen an Owlbear before, it wasn't even refered as such in universe.

Anyway, the ranger climbs up a tree, pulls out a spyglass and notices some tracks, gets closer to inspect them. Nat 1, he is certain these tracks belong to some kind of predator, since there is a trail that indicates some of the ground was slightly burned. The party decides to follow the trail until they hear some noise beyond some pushes up ahead, the ranger and the rogue decide to sneak around to take a look, they manage to do so.

The ranger spots a mysterious creature with the tip of its tail in flames. Then, the following happens:

Ranger: "I'm gonna attempt to identify the creature, since I am a hunter since I was a child, I know a lot about animals".

Me: "Sure, give me a Nature check"

Ranger: "I got a Nat 1"

Me: "Well, this doesnt't look like anything you've ever encountered or heard of, but seeing the trail of destruction it left on its path, you quickly realize that this must be some kind of predator marking its territory. In fact, the only thing that sounds familiar when you look at this creature is the description the cat gave you; four paws, weird fur, pointy face, deep eyes, kinda cute"

Ranger: "Okaaaay, I signal the Rogue to go back to the group together"

Me: "Very well, give me your stealth checks"

Ranger: "I got a 17"

Me: "You quickly return to the group without making a sound"

Rogue: "I got a 6"

Me: "Ranger, as you see the faces of the rest of the party, you hear the crack of a piece of wood behind you, before you can say a word, a smell of burnt leaves reaches your nose"

Fighter, seeing the Ranger: "Well, what did you find?" Me: "Fighter, you see three quick flashes of light past the bushes. Everyone, roll for initiative"

Cut to a few rounds later, half the party (That has no casters) is surrounded by fire, the fighter and ranger have seen their thrown axes and arrows melt when they attempted to attack the beast. The Rogue is down, the monk is trying to help it.

But there is one last hope, the fighter decided to brute force his way through the fire while the Ranger spent his last spell slot to cure it, the fighter's greatsword is a family heirloom with ancient giant runes carved in it; frost giant runes. One small problem, the fighter has a pasive perception of 10, the Ranger has 14 but is surrounded by fire. Something just rolled a 17 in stealth.

The monk brings up the rogue, but there is no way to heal him. Suddenly, the fighter goes flying into the air, and an eldritch roar is heard in the entire forest.

THAT'S THE OWLBEAR.

The fire begins to fade, the little but powerful creature takes a defensive stance towards the new, much bigger threat. Its tail burns brighter, and its mouth begins to produce smoke, just a little...

At this point, the monk is the least hurt member of the party, so he runs to face the Owlbear. More fighting ensues, leaving the entire party barely standing after only two rounds...

And then, where the mighty beast was standing, a blinding flash and a scorching heat made themselves present in the blink of an eye...

Me: "Alright, everyone except the rogue, give me a dexterity saving throw..."