The possibility that leapt immediately to mind was giving a planet the system-grav-shield function, sealing the system until whoever's trapped inside develops tectonic disruption weapons powerful enough to destroy it. A pity the AI isn't very clever, one could set up a cute "ancient evil sealed away by ancient foes" scenario with the ancient evil breaking out of their ancient prison to menace the younger races. A human could play that role in PBW, though.
I suppose you could give it to a sun as well in that case, so that anyone trapped inside has to commit suicide in order to free themselves. But that's kind of pointlessly mean.
Oh, on the other hand, one could use the map editor to make one-way warp points leading into such a "sealed" system. Kind of an interesting situation for the crews; they'd better hope there's a colonizable planet in there.
Re: Stellar Manipulation Suggestion for 1.42
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