The Adventure Barrier is a gate that was added in The Adventure Pack Strikes Back! Update.
It acts like a Dragon Gate, where players can punch it to either open or close it. However, when an Adventure Brazier is lit up in the same world, the barrier will either open or close. Open barriers will close, while closed barriers will open.
Note: You can't drop items on an open Adventure Barrier, unlike Dragon Gates, which allows you to drop items on it when it's open.