Butterflies

If there were any real butterflies around, the name would be confusing, but I'm not talking about insects here. You'll wish I was. Butterflies are part of What lurks in the Mist, a special breed. If most of the things in there are unchanging terrors beyond our understanding, at least they are unchanging. Butterflies are not like that. They learn, which is worse.

Unfinished job

You know how when you get bruised by something and escape with your life, you will heal and come back stronger, learning the lessons of your previous encounters? Take the same idea, but several notches higher and you have butterflies. We call them this way because they not only learn, they change. Evolve. And usually, they come back immune to what wounded them, with a knack for finding their nemesis. The second encounter rarely goes well for us, mind you.

Basically, when you fight a monster inside the mist, always go for the killing blow, even if it means taking risks. Better hurt now than dead in a month, right? And don't think you'll be able to best the thing a second time, because you may not even recognize it. When I say they change, I mean they assume completely different forms, usually bigger and stronger, but sometimes thinner and more cunning. Now for all we know they are exceptions rather than the norm inside the Mist, but you really don't want to take that bet.

Scarface

We had to discover them the hard way, with the infamous Scarface. It was a rather inconspicuous thing, a humanoid monster among many, not even strong enough to be a threat to Pascal Sterling, who cut its eye and barely split its body in two. We didn't see it again for months, and quite frankly nobody even thought it was noteworthy. The next time, it had become a strange abomination, the silhouette of a butterfly but the size of three men, with a giant scar barring its avian face. It went straight to Pascal, who fended it off once again, adding a new scar on its forehead and cutting off an arm.

The third time was when it slaughtered Pascal and her group. With two scars and a stump arm, an arachnid as high as a three-story building rushed inside the city, destroying many buildings before reaching its nemesis. This time, it required the combined effort of many to repel it. Since then, it appears from time to time, always donning a different appearance, never letting go of the scars that made it famous.

So long story short, don't let the things of the fog escape, or they will come back to bite your ass. And their mouth will be bigger than you.