It's a new feature where you can create an unbreakable barrier. This is similar to
I'd suggest that for this card to be at all functional it needs one key elemental restriction -- that the card only works if it doesn't separate a territory from the rest of the map. IE the card will always work unless it's cutting off a territory from the rest of the map. So that all active territories always some have means of connection so it isn't possible to permanently wall yourself off. With that limitation this card could be interesting as it's like altering the map mid-play. Perhaps a way to create them from the get-go in a custom/scenario game as well instead of the current working which just has people creating really large neutrals for the effect. Which is generally basically the same, except it can't be done during game without large army commitment which makes it different in a significant way.
So if you don't want to lose, you wall off one territory as unbreakable, and live there forever?
I agree with this idea fully, even if it does seem to have been stopped mid-thought.
coupled with the scenario's Idea, this would be useful... want to create a war between Spain and France? make those territories into ownable, and block off the escape routes... is greater then ridiculous wastelands only in the instances when you use AI, as they will build to break, no matter how incredible the size is...