Nebulas are regions of space that are impassable to starships. Ramjets can only be built and move within nebulas and play same roles that starships play in open space.

The resources aetherium and chtholon can only be found on special planet classes found in nebulas.

Bright nebulas generally only contain aetherial, empyreal and nebular worlds. Fleet visibility is reduced by 50%.

Dark nebulas can contain any class of worlds except aetherial and empyreal. Fleet visibility is reduced by 75%. In future eras, direct attack damage will reduced by 50% and missile attack range will be reduced by 25%.

Found only in dark nebulas, transpace rift nebula zones are totally impassable to fleets. Fleets may be able to navigate through gaps in the rift zone.