In the Hobbit, Bilbo saw that in the Woodelven palace/castle, there was a magic gate. It only opened for Elves, and he couldn't find where it opened. So I'm proposing magic gates.
They would look just like normal gates, onto you can't click them to open, instead, you must have 100+ alignment with Mirkwood (or be an elven NPC), and get within a one block distance of item while facing it. It would open up, and once the person/NPC gets 4 blocks away, it would detect if there are any players/NPCs within a three block radius, in which case, as long as they are look at it, it would stay open for another 3 seconds. This is so the door won't keep closing while moving a spread out army through.
It would work by having it detect where players and NPCs are, and what direction they are looking. Though if a player of NPC just stands near to it, and does t go through but occasionally looks at it, it would eventually not work for that NPC/person, until they leave the general vicinity and come back.
I couldn't think of a crafting recipe for it, though.