Dark Barrier

Appearing only in Four Swords Adventures, these Dark Barriers are created by Vaati, and block the exit from every level. The barriers can only be broken by powering up the Four Sword, which is achieved by collecting 2000 Force Gems within the level. The barriers are always composed of four glass globes containing the eye symbol of Vaati, connected by a chain of electricity and surrounded by a dark fog.

The barriers (according to Kaepora Gaebora) drain the land of its life, similar to the Twilight Curtain.

Trivia

 * The Dark Barriers are very similar to the barrier that blocks the top door of Hyrule Castle in A Link to the Past, which link must hit with the Master Sword.