Decomposites
Decomposites are alchemists' pets, created to assist in the breakdown of minerals. However, it was hardly possible to keep track of every tiny bit of slime, and some inevitably escaped captivity.
In their base forms, Decomposites are blobs of translucent slime of varying colour, containing a nearly ever-burning flame. The colour of their flames is not dependent on the colour of their slime, and can be anything. A Decomposite's base slime colour, and flame colour, will remain consistent throughout its life.If a Decomposite has not absorbed a fuel for their flames, those flames will slowly burn through their own slime mass. A slime that has burned itself down into approximately the size of a softball will not be able to burn itself further, until it has either replenished its mass or consumed fuel. Its flame will go out until then. However, it can still be burned by external sources of heat. This is the only known way to entirely destroy a Decomposite.Decomposites' flames only fully go out when their bodymass has burned down too much. Curiously, even in an environment devoid of oxygen, their flames will remain ignited.Decomposites absorb rocks in order to break them down and extract specific elemental materials from them, which can quickly change their appearance, as their slime becomes filled with bits of the rocks they've eaten. While the minerals are inside of the Decomposite's slime, it is able to separate those minerals into their base components with extreme precision, latching onto the element[s] it wishes to extract at the molecular level. The slime is an inert substance, in which elements are stable; no unintended chemical reactions will occur to materials encapsulated within it.Mature Decomposites will typically form a crude skeleton to better support the weight of their bodymass, as they are heavier once saturated with mineral buildup. This is most commonly done by densely amassing many bits of metals they've extracted within themselves, arranged into the bonelike shapes they desire, but with a hollow channel left in the middle of these bonelike structures. Intense flames are then blasted through the hollow centers of these "bones," melting the metal bits together into a strong alloy. This also, however, burns the slime that is holding the molten metal in place, thus leaving a coating of dead, darkened slime fused to the outside surfaces of these metallic "bones," that the Decomposite may or may not bother to scrape off. A bit of the underlying metallic sheen can often be seen through this tinted coating. After the metal has cooled, living slime will typically fill the hollow centers of the "bones," to most effectively hold onto them and puppet them into their desired positions.
A Decomposite's slime mass is like a continuous muscle. The more solid slime it is, the stronger the bond between all the slime is, the stronger it thus is overall. The more saturated with minerals it becomes, the weaker it becomes, because the slime mass is broken up by all the little pieces of rock it's holding onto. Therefore, there is a benefit to the Decomposite keeping at least part of its body pure slime. More saturated slime is more drippy/oozey, and requires a sturdy skeleton to assist in holding its preferred form.By default, a Decomposite will prioritize seeking combustible materials, to maintain and strengthen its own flames.Decomposites are fully sentient, they have intelligence comparable to a human. They can be dumb or smart by more or less human standards, but they are not animalistic in mind, in spite of whatever appearance they choose to take.The spark of life that animates a Decomposite had to come from somewhere. Could be an animal, could be a large amount of plants. The latter is less common, as it is a less efficient source; while it takes many plants to provide enough life energy to sustain a Decomposite, a single decently-complex animal organism is often enough to do it.The maximum size of a Decomposite is determined by the complexity of the organism that "donated" its energy to the creation of it. The more complex the organism, the bigger the Decomposite can potentially become. [Humans are, unfortunately, quite ideal donors. At least if ethics are not considered an issue.]A Decomposite may or may not have the memories of whatever was killed to create them, depending on how stubbornly the soul of the old owner of that energy remains holding onto what was once theirs. The Decomposite is not a reincarnation of this entity, but it may more or less be slightly possessed by it.
key features:
Decomposites can take any shape. They are slime that can change their form at will.
Decomposites can be any colour[s]. Their base slime colour + flame colour can be anything, and they can adorn themselves with additional colours depending on what minerals they absorb.
They glow faintly. This is most evident when their flames are out, a small amount of light is emitted from the slime itself.
Mature Decomposites' skeletons can often be at least partially seen in some way. These skeletons are typically metallic, often [but not necessarily] with a coating of darkened dead slime on them, which will thus tint the metal that colour. This tint can be anywhere from barely visible to nearly opaque, depending on the thickness of the coating.
Metal adornments are common fashion choices
Their "eyes" are holes, which their internal flames can be seen through. Their pupils, if they have them, are small white lights that float in these holes.
Decomposites can:
Take and use the bones of other Decomposites [whether these bones are given up willingly for whatever reason or stolen], seeing as they are not living parts of the Decomposite that made them
Craft metal alloys and glass, as they can refine both elemental metals and silica, and produce fire
Exist underwater. They will not dissolve, and their flames will not go out. Their heat will, however, boil the water around them.