I am writing a story set in a modern world where D&D magic works. Now, I also have a Cheyenne Mountain like set of facilities in my world, underground hardened military airbases. Obviously, you don’t want any old bloke to be able to just use the Etherealness spell to waltz in through the walls and steal a nuclear warhead. You also don’t want the enemy war leader to be able to see inside your war room. And teleportation would really be a security disaster. Could the unit’s mages cast Mind Blank on every single one of the 570 staff of the base?
I had a couple ideas, using a multiple castings of or a homebrew larger version of the Forbiddance spell to cover every cubic foot of space inside the mountain and a similar method with Anti-Magic Field around the boundaries. This seems to block anything short of divine intervention, but I was thinking of asking you folks here about ideas as well. Would my idea work? Do you have any suggestions? Perhaps a magic item that could do the protection?
I’m not concerned as to which version the spell/item comes from.