[Taqwus]

Something that would be truly evil would be a cloaking facility -- placed at somewhere like Cloaking 4 (at a minimum...), acting as a Cloaking 1 device for colonies so you'd need sensors to find it in the absence of other clues.

The colony would be considered 'blockaded' when cloaked (does not contribute any resource, intel or research to the Empire, and builds at a slower rate, since the shipping et al would give the colony away), plus would need to uncloak for a full turn to interact with the owner's ships (cargo transfer, repair, etc). And it'd be revealed if somebody explicitly attacked that sector, tried to colonize it, etc.

Purposes would be --

a) hiding if you're getting seriously beat-down, in the hope that either allies or dwindling supply forces your enemy to abort the search

b) setting up a concealed outpost near or in enemy space, and then only revealing it once you have defenses in place

Can of worms, but could be an interesting can of worms.

------------------
-- The thing that goes bump in the night