I had an idea for a herd animal that was born and lives in space and travels like whales in groups.

These creatures would be in Solar systems with with a large active sun and dense asteroid belt that's rich in both minerals as well as biological residue on the rock and take the form of armored whales with mouths akin to the star nosed moles.  Upon "Bumping" into an asteroid there would be a chance of it being one of their eggs causing them to attack you by surrounding your ship and latching onto your fleet killing crew members as they drain your energy & biological materials as they attempt to eat you to death.

To be rid of them you would have to "bump" into another asteroid to knock them off, or potentially shoot them off or sacrifice the ship(s) in question.  The payoff for defeating the creature would be raw materials including a few rare materials and biological data as well as the potential to study the natural armor on them to re-enforce the ship(s)

This race could also potentially be in fleet battles and drain both Crew & Battery until your ship dies while slowing down the ship and hindering the ship's maneuverability the whole time.  To remove the debuff you would have to bump into a moon/planet/asteroid, or your opponent shoots it instead of hitting you as intended.