project Seblin
Since the poisonous dragons have the ability to create acid, they decided to take their capabilities of cell destruction to another level. They wanted to create something that could steal cells and rearrange them to make itself bigger. Something that could not be destroyed by firing bullets or cannonballs at it. Something that rendered all advancements of war useless. Something that was sentient enough to protect their land efficiently, but that was blindly loyal.
project Seblin is a creature made of black tar and ooze. It is capable of rearranging cells and making itself bigger. It was created by the poisonous dragons, in an attempt to create a creature that could defend them, unfortunately, they made it sentient, which was their goal, but you can't make something sentient without giving it instincts. It is a creature like any other, and it's only goals are to survive and grow, like any animal. When something gets stuck in it, it holds on and becomes sticky, and it starts to dissolve it. It was created on one of the poisonous dragons smaller islands, so when it broke out of the lab, they just abandon the island, since project Seblin can't swim.
Unfortunately, as time went on, it grew smarter, and learned how to split itself into multiple pieces, as well as how to take a more solid form. It noticed the birds that would sometimes land on the topmost branches of the trees, and it tried to mimic what it saw. Eventually it was able to create a solid body and sustain it. At this point it had also learned how to form tentacles that it could shoot out and grab things with.
Project Seblin is blind, but it can detect movement. That's how it 'sees'. It can sense the vibrations in the air and in the ground caused by the movement of living creatures. It doesn't understand color or sound, which is why it never changes color, and thusly can't efficiently impersonate someone or something. If you were to stand still, project Seblin, in theory, wouldn't be able to detect you. How do you get away you may ask? You don't. Unless project Seblin moves away from you, your stuck where you are. However, if there was some kind of constant movement, like a very windy day, you may be able to slowly move away without project Seblin detecting your movement among the other vibrations.
Since project Seblin sees by vibrations, sound waves would have the same effect. If you were to play a recording, project Seblin would attack it as if it were an animal. Since project Seblin senses sound waves the same way it senses vibrations in the air and ground, echos would confuse and disorient it. If you were in a cave, for example, you could shout and yell, and project Seblin wouldn't be able to track down the origin of the sound waves, allowing you to escape. You could be completely alone, but project Seblin would assume that there were somewhere around ten or more people. Project Seblin also can't copy your appearance unless your moving, and even still, it takes quite a while for it to fully take your form.
Project Seblin was eventually contained in a crystal ball by the magic of the prosperous. The prosperous's magic comes from their talismans. The objects that helped them defeat the silver savage.