Protean

Proteans, sometimes known affectionately as "Morphs" are a species of slime-like creature native to the planet of Proteus I.

Biology
Proteans, in their resting state, appear as blobs of thick goo without any discernible organs or biological systems. This goo can come in nearly any color with varying levels of translucency, and ranges from translucent pink, to opaque teal, to a black sludge, and even to clear and water-like. Proteans early in their life are capable of flight, being able to levitate through the air effortlessly. However as a Protean grows in size and matures, it eventually loses this ability and is forced to use other means of locomotion. By far the most distinctive features of Proteans is their ability to alter their shape, texture, and vocalizations to mimic pretty much anything of similar size. However while a Protean can mimic the appearance of tougher substances or stronger creatures, they still retain their weak strength and fragile structure. That being said, Proteans can simply reform themselves when dismembered or injured, and killing one requires the complete destruction of their entire mass via digestion or vaporization. As expected, Proteans eat by enveloping their prey and slowly digesting them within their mass, similar to an amoeba. As a Protean grows in size, it becomes capable of reproducing via mitosis. However if a Protean instead continues to grow in size, it becomes stronger and more intelligent. In a few documented cases, larger Proteans have even been shown to not only mimic intelligent races, but have also displayed full sentience when exposed to higher civilization.

Counter-Tactics
Due to their perceived invulnerable form and near perfect mimicry, sentient Proteans are listed by many biologists as one of the galaxy's most dangerous races. However they are not without weakness. Regardless of their appearance, they are still made of a thick slime and are incapable of doing much physical damage in unarmed combat: their danger coming from enveloping their target and suffocating them. In addition, they are prone to freezing as a way of temporarily restraining them. On the opposite end of the spectrum, extreme heat can break down their cellular structure and disintegrate them. While kinetic, explosive, and melee weapons are all but useless, energy weapons are a good way to chip away at their mass. While on the surface Proteans are nearly impossible to tell apart from other species, they do not give off heat signatures and, like Calatians, can be rooted out through thermal imaging.