The Tahmk are of short stature, averaging circa 130 cm in height. Due to their small form, they are usually very energetic and tenacious. Their faces resemble that of humans but they lack noses. they have dark eyes with double eyelids, one of which is transparent. Other notable features are their fin-like ears which seems to be a evolutionary left-over from their aquatic origin. They do, however, still have functioning gills along their necks, webbed feet, scaly skin and rows of shark-like teeth in their mouths.
They have only one gender but are usually described as young males and mature females, referencing their outward appearance. The Tahmk hatch from eggs as males, part of a group of up to 30 individuals. After reaching maturity, usually in 1,5 to 2 years, he will start to secrete pheromones, which will signal a fully mature female that mating is possible. The female will then mate with the male by vomiting a seminal fluid into his stomach which contains tiny spores. The spores will latch onto the walls of the males stomach and lay dormant until it's host dies. The spores will then consume the body and morph into eggs, which then hatch out of the corpse to begins the cycle anew. When the spores reside on the walls of the stomach, they produce hormones that gives the Tahmk increased strength and heightened senses. This will also, appearance-wise, transform the male into a female.
Their species are very adapt at surviving many perilous hazards due to their original environment, but can also adapt according to their environment thanks to short life-spans and a great birth to death ration. The Tahmk are cannibalistic, but can eat almost any variety of meat.
They are considered semi-sentient by the scientific community, due to their limited cognitive abilities and a dominant feral instinct. They possess a rudimentary clan-based culture, which is mostly dictated by genetic relation more than principles, and the clan is usually ruled by brute force by a single, Prime, individual.
They are a predatory species and are very savage in their nature. A researcher once said, "They are fascinating yet despicable creatures. Imagine if you had a dog that could talk. Now imagine that you gave that same dog rabies and thought him how to operate firearms."
Tahmk are only seen off of their own planet when they are "employed" by pirate bands. Accepting simple payments such as food and firearms, Tahmk groups can be controlled by a single individual whom then becomes their Prime. A single Tahmk can be a dangerous, but manageable. A group of aggravated Tahmks is a life threatening situation. If the group perceives weakness in their Prime they can, despite their lack of social unity, overpower the Prime and kill it.