Abyormenite

There are two distinct sapient species inhabiting the planet of Abyormen, both of which are commonly called Abyormenites. Abyormen is a planet with a highly unusual orbit around a binary star system. Basically: it orbits the red dwarf star Theer, which in turns orbits a blue giant known as Alcyone, or Arren as the natives call it. This creates a unique seasonal cycle consisting of two alternating periods: a "hot" season and a "cold" season, each lasting for approximately 65 Earth years (830 local years). The two races peacefully alternate inhabiting the planet, one being active during the cold times, and the other during the hot times.

The "hot season Abyormenites" are radially-symmetric, thermophilic beings, while their "cold season" counterparts have a fairly humanoid appearance. Although radically different, both races are about the same size (4.5 feet, or 1.3 meters tall) and speak the same language. Also, they both have a similar social structure, with a selected group of individuals remaining alive through the adverse season to act as Teachers to the new generation, once it is born.

Reproduction
One of the most interesting aspects concerning the lifeforms of Abyormen is the way they reproduce. This happens only during the passage from one season to another. Both Abyormenite species reproduce in a way analogous to bacteriophage viruses on Earth: by laying reproductive spores inside the cells of other creatures. When the "hot season" comes to end, all "hot Abyormenites" die, and the new generation of "cold Abyomenites" start emerging from their bodies, in which their ancestors had left their spores 65 Earth years before. During their life, these "cold beings", in turn, carry the dormant spores of their "hot" counterparts inside each cell of their body. And when they themselves finally die at the end of the "cold season" it is the "hot Abyormenites" who emerge, completing the cycle. As a result, both races are so deeply linked to each other in this symbiosis that they depend upon the death of each other to reproduce.

The same process happens with all animals on the planet, except for a small fraction that leaves their spores on the soil. The problem is that, since no reproduction takes place during the "seasons", only between them, it is important for all species to keep their population from decreasing too much. For that reason, all life on Abyormen has amazing regenerating abilities. Not only injuries are healed and lost members grow back, but most importantly, whenever an animal is killed by a predator or by accident, its remains will regenerate into one or more new individuals.

"Cold season Abyormenites"
During the 65 Earth years long period of relative coldness, Abyormen has an oxygen-rich atmosphere and is inhabited by short-statured humanoid beings. They appear to keep growing through their entire life, but except for the Teachers and for those who had suffered accidents and had to "start over" (regeneration), all Abyormenites at any given time are of the same age, and hence of the same height, since they are all born in the beginning of the "cold season". They live for this whole season and then all die, with an age of 830 Abyormen years (which is 65 Earth years) and a height of 4.5 feet.

The Teachers, however, are those few Abyormenites chosen to remain alive through the "hot season", hidden inside ice caves in Abyormen's southern ice cap. Because of this, the Teachers can grow up to 8 feet tall. Their main purpose is to act as mentors to the next generation of Abyormenites that will be born, once the next "cold season" begins.

Abyormenites are omnivores and are able to stand a wide range of temperatures and pressures (though they prefer cold environments – obviously). It is even possible that the main reason they die during the "hot season" is the change in atmosphere, rather than temperature. They are also notable for their ability to spend several days without food or water.

Abyormenites have claws on their hands and feet, rendering them excellent climbers. Their eyes move independently, like those of a chameleon, allowing them to look in two different directions at the same time. They see light in a different spectrum than Humans, being able to see infra-red, but not violet. They also have an extremely acute hearing, despite the lack of visible external ears; and an exceptional photographic memory.

"Hot season Abyormenites"
The beings that inhabit Abyormen during the "hot season" are astonishingly different from the "cold season" ones. These Abyormenites are radially symmetric creatures, with a melon-shaped body supported by six strong tentacle-like legs. Their appearance has been described as being similar to a fat-bodied starfish walking on the tip of its arms. Their mouth is on the top of their body and they have sets of small manipulatory tendrils on the tip of their legs, which are normally retracted when not in use. Completely eyeless, they actually see by means of high frequency sound waves.

They can only survive in extremely high temperature and need an atmosphere rich in nitrogen oxides, with nitric acid for moisture. During the "cold season", their Teachers survive underground near volcanoes.

"Hot season Abyormenites" are far more technologically advanced than the "cold ones". Their cities are equipped with electricity, though not electric light, as they are not able to see lights of any kind. In spite of their use of echolocation instead of eyesight, which makes them unable to see anything outside their planet's atmosphere, these Abyormenites are able to feel the presence of the two suns and have a basic notion of astronomy. They are rather afraid of science, considering too much knowledge to be dangerous, and their Teacher will often try to avoid any technological advance that may lead to space flight. This is because they fear that if someday either them or the "cold ones" leave the planet this will be the end of their symbiosis, eventually leading to both races' extinction.