When you cast this spell, you erect a barrier of energy drawn from the realm of death and shadow. This barrier is a wall 20 feet high and 60 feet long, or a ring 20 feet high and 20 feet in diameter. The wall is transparent when viewed from one side of your choice and translucent—lightly obscuring the area beyond it—from the other. A creature that tries to move through the wall must make a successful Wisdom saving throw or stop in front of the wall and become frightened until the start of the creature’s next turn, when it can try again to move through. Once a creature makes a successful saving throw against the wall, it is immune to the effect of this barrier.