The Hreem are a species of multicellular hive-based prokaryotes that invade and terraform other worlds for their own purposes.
The Hreem vaguely resemble black-carapaced insects, but are in fact members of a fourth taxonomic domain known as Multiprokaryota. Multiprokaryota are divided into the two kingdoms of Multibacterioida and Multiarchaeoida. The Hreem are Multibacterioida. Unusually for prokaryotes, they reproduce sexually. Hreem are chemotrophs that oxidize hydrogen sulfide into sulfur for energy and use low quantities of oxygen as an oxidant. This last quality makes them microaerophiles. The Hreem take in hydrogen sulfide and oxygen through thousands of tiny spiracles. All Hreem except for Caliphs have six limbs, but the number of eyes vary.
The Hreem are a hive-based species divided into six castes, each with a specialized function.
Eunuchs are the workers and soldiers of the Hreem. A eunuch is a large, bulky Hreem, about eight feet tall, with four arms and two legs. Its upper arms are like those of a mantis, with five-foot scythes studded with six sulfur spikes on the inside. Its lower arms have two downward-facing humanoid hands with five spindly fingers used for grooming eggs and for fine manipulation. On the back of the eunuch's hands shoot out small shards of sulfur, which functions like an extremely powerful sandblaster. Eunuchs have digitaroid legs with two sulfur-tipped claws on each foot. Its mouthless face has a diamond pattern of four compund yellow eyes with a fifth eye in the center. They are the only Hreem to be able to exist outside the hive for a substantial period of time because of their ability to seal their spiracles and six crystalline bubbles on their back that store hydrogen sulfide as food on the hoof. Eunuchs are male and completely sterile.
Concubines are next up the Hreem heirarchy, being the mothers or sisters of the eunuchs. They have a triangle of compound eyes on their faces and have two long antennae. Concubines are the most humanoid of the Hreem, but do not appear female. Their upper and lower arms are identical, with six fingers tipped with crystalline sulfur claws used as weapons. Concubines have the same leg structure as eunuchs. They are female but appear androgynous; they are feminine in structure, being rather streamlined, but appear masculine due to their seven-foot height and lack of mammaries. Their most prominent feature is a large, thick ovipositor that resembles a tail.
Hreem princes are juvenile Sultans, and like their fathers resemble centaurs. They are ten feet tall and twenty feet long, with half of their length coming from a scorpion-like tail ending in a sulfur-tipped stinger, used to inject sulfuric acid into enemies. Their upper bodies are humanoid but not yet muscular, and their heads have two vertical rows of three eyes each. Its arms and legs end in four powerful claws. Princes gather groups of concubines of their generation in preparation for building a hive of their own. To prevent incest, princes are born from unfertilized eggs.
Sultanas are very old concubines, who are no different from their juniors except for their size (twelve feet tall), double ovipositors, and ability to birth princes. Princes generally defer to sultanas, who generally ignore their offspring in favor of their mate. They sometimes kill concubines out of what is best described as jealousy.
Each Hreem hive is ruled by a sultan. A sultan resembles a prince, but it appears far more muscular and has a huge head crest similar to a Triceratops. It is twenty feet tall and forty feet long, and it has an extra row of eyes. They mate with a harem of concubines and sultanas to produce eunuchs and more concubines, which then mate with princes.
The Caliphs are sultans who have lived for an unknown amount of time and have metamorphosed into something much greater still. They are sterile sultans so massive they can no longer move under their own power; a Caliph is approximately five hundred feet tall and wide. Their limbs were lost in the transformation from sultan to Caliph, and they now resemble enourmous heads rooted to the ground with thousands of tendrils. A Caliph's "face" has ten rows of ten eyes each. They are far from defenseless; they have four tentacles sprouting from the back of their "heads" which shoot out streams of tiny, dense sulfur shards that can blast through solid rock like a sandblaster through butter. Despite this weaponry, Caliphs generally rely on their lessers to do the fighting for them, and they are the deities of the Hreem. The seven Caliphs rule as equals from a massive hive-palace on the Hreem homeworld, a planet aptly named Sulfuris. They are willing to go to great lengths to prevent other sultans from becoming Caliphs.
Hreem have a relatively complicated life cycle. Concubines and sultanas mate with the hive's sultan, producing eunuchs and a new generation of concubines, and sultanas occasionally lay eggs asexually, which hatch into princes or concubines ready to replace the "old batch," as sultans live far longer than concubines and incest would result in the species' eventual destruction. The princes then gather unrelated concubines of their generation in preparation for their transformation into a sultan. Once completing their metamorphosis they are promptly driven out, beginning the cycle all over again.
Eggs are laid in a set of seven rings surrounding a Hreem Xenoformer. Normal eggs develop into concubines (1st and 2nd ring) and eunuchs (outer rings). Unfertilized eggs develop into princes (1st ring) or concubines (2nd ring).
Hreem live for varying amounts of time depending on their caste. Eunuchs reach adulthood at 1 year and live for 40 years. Concubines become adults at 1 year of age and live for 100 years, the last 20 years of which they spend as sultanas. Sultans spend the first 5 years of their lives as princes and are biologically immortal. However, they self-terminate at the age of 500 due to the commands of the Caliphs. Caliphs do not age.
Hreem hives are massive structures the size of cities on the surface and much, much larger below. The surface portion of a hive resembles a series of towers and domes carved from stone. The inside of a hive is filled with hydrogen sulfide gas mixed with low amounts of oxygen. A vast central chamber contains the sultan. The hive is dotted with Hreem Xenoformers.
Hreem Xenoformers are lithotrophic organisms that excrete hydrogen sulfide. The Hreem cultivate them and use them to xenoform planets to make them more habitable. They resemble 20-foot-wide hemispheres of black flesh covered with spiracles through which it excretes hydrogen sulfide.
Hreem ships resemble five-mile-long segmented worms. They are capable of space flight and are the main transport method for the Hreem.
The name "Hreem" is based off of the word "harem," which is what their reproductive structure is based off of.