User blog comment:GrandMethuselah67/Lore Sheet: The Democratic Imperium of Neohumanity/@comment-4867780-20150916222115/@comment-4867780-20150917063705

I was mostly thinking about imperialistic planar superpowers several steps ahead of the Imperium, and major extraplanar predators drawn to all this planeswalking the way daemons from W40K are drawn to psykers.

Admitedly the odds are extremely low, but on such a gigantic scale it's almost guaranteed to happen on a regular basis, even with a strictly low-profile policy.

It's true the mix of negociation/detterment and powerful defenses / reliable evacuation should considerably dampen the risks and consequences, but if the other side is substancially more advanced/powerful they would have no trouble hunting the Imperium down and finishing the job.

At any rate, it's definitely not something I would allow in OZ's place ^ ^;