Quantum Lice:
Generally a nuisance and can infest ships. Their unstable nature makes them hard to predict, and each type requires an unusual method to deter and expel from a ship. Top, Charm, and Bottom lice have no known deterrent, but are rarely ever seen. Up, Weird, and Down lice are much more common. (I'll think of methods to deter them later)

Dust Slime:
Simple cosmic hitchhiker, often hiding in nooks and crannies on the outside of ships or in cargo bays and ventilation shafts when they aren't attached to space debris.

Solar Slime:
Rarely found in the corona of stars. They usually have little interest in ships but can burn a hole straight through a hull if a pilot isn't careful.

Comet Slime:
Harmless and simply content at drifting through space

Dust Giant:
Harmless and usually invisible to the naked eye unless it is hit by solar winds which ionizes it, displaying beautiful colours. They can range in size anywhere from a couple meters across to planet sized. Their life cycle is completely unknown as it is believed that they mostly live in space between stars where they cannot be seen or detected.

Prophetic Carnilith:
Only two have ever been sighted in modern records, none sampled. They appear to have a strong psychological impact on organisms close by, and have appeared in mythologies around the galaxy as an omen of apocalypse.

Shroud Wraith:
It is believed that one directly looking at you means inescapable death. They are only ever seen in the Shroud but once you are spotted by one, it is too late. It is not as simple as avoiding being seen, as spending any amount of time in the Shroud risks you being seen whether you think you are hiding or not. Some people may be spotted within a few minutes, some have spent countless years on expeditions in the Shroud and have yet to be spotted.

Echo:
Unknown and seemingly harmless, if not very unsettling. They have been seen many times but none have been able to be researched. Their unique shape is described in ancient mythologies around the Constellation (all the planets/stars that I draw)

?:
An unknown metal that has been described by many civilizations. Descriptions claim it has some form of unknown intelligence, and is only ever seen in one place at a time in the entire universe, capable of vanishing without a trace at any moment. Its current location is unknown