Death angels are a race of bioengineered battle-creatures from the Sentros Galaxy. They are sophonts, created by Starbuilder bioengineering technology (which, unfortunately, self-destructed soon after the death angels left the planet). They are treated as holy by most Starbuilder-worshipping Kar'lul. Despite their fearsome name and reputation, death angels are not naturally aggressive towards other races.
They were created when a group of pirates discovered a working Starbuilder bioengineering facility, and decided that the Starbuilders had gifted it to them for them to use as they saw fit. The facility presumably detected that the pirates were attempting to create a violent servant race, and their creation- the death angels- easily slaughtered them. The death angels escaped the self-destruction of the facility by stealing the pirate shuttle, and were found and taken in by the Alliance of Kar'lul Colonies, who saw them as angels of the Starbuilders that punished the unrighteous.
Death angels communicate using biological radio. This meant that they require radio-sound translators to interact with other races, on top of normal translators. They tend to be irritated by the voices of other races, and so are relatively isolationist. They have a biological caste system, with the Queen laying the eggs of whichever caste it needs.
Bioslick, and its derivatives, are the only caste that are never laid by eggs. Instead, it is a grass-like photosynthetic organism that grows from spores released by all death angels. Bioslick can detect the lack of a Queen, and will grow a new Queen from an egg if there is none. This makes it a problematic substance for inter-race diplomats, as bioslick spores can result in a death angel hive being grown. People going either on- or off-world have to go through thorough decontamination procedures. Their photosynthesis is one of the most efficient ways of photosynthesis known to science, far exceeding every other known plant in the Sentros Galaxy.
Death angel hives are created by bioslick when the presence of a Queen or a Queen egg is detected. These massive structures can be as large as entire cities, if not larger, and are designed to sustain an entire population of death angels. These extend both deep underground and high into the sky. Entrances are covered with gun-growths to defend against intruders (although technological systems are preferred).
The bullet caste is made up of tiny, non-sentient parasites. These are laid by gun-growths, and grow inside a fleshy ammo-pouch. When the pouch contracts, the bullet castes enter the firing chamber, and are propelled at high speed to pierce and dig into the foe. Their heads are needle-shaped, but these snap off inside the target to facilitate burrowing in the flesh. Once the foe is dead, the bullets gather in the core of the organism and merge into a single creature, eventually growing into a leafy, photosynthetic turret if not removed. Bullets can be moved from one creature's gun-growth into another. Bullet-castes produce bioslick spores, meaning that having the bullets removed before they do too much damage can result in being eaten from the inside by bioslick roots.
Workers are the most common of the sapient castes. They tend to the hive and bioslick, collect food (both on and beyond the bioslick), tend to other castes and alert others to danger. They also tend to do the jobs that warriors are too large to do. They have twelve limbs- six legs, growing from a horizontal body, as well as four arms on the front of the body and two limbs supporting gun-growths. Workers produce bioslick spores, and are about a metre long.
Warriors are similar to workers. They are much larger, however- reaching up to four metres in length- and have an extra pair of gun-growths instead of normal arms. Their much larger size means that they are both more proficient in combat and can do heavy lifting that workers cannot. Warrior castes do not produce spores, meaning that most off-world death angels are warriors. They usually turn into Queens when separated from other castes, however, so they require hormone treatments to prevent this.
Queen-castes are largely immobile, and lay the eggs of both workers and warriors. As they are derived from warrior-castes, they have four gun-growths and two arms. Queens, when outside a hive, will produce spores. The bioslick growth will then grow a new hive around the Queen. Warriors sent away from a hive will become Queens, ready to start a new death angel hive. This caste is the largest, reaching 6 metres in length.