The air before you shimmers as it suddenly hardens. You create an invisible wall of air, bonded by magical energy. The wall appears within range and lasts for the duration. You can make a straight wall up to 15 feet long, 20 feet high, and up to 5 feet thick, or a ringed wall up to 15 feet in diameter, 20 feet high, and up to 5 feet thick. The wall is transparent, but provides full cover from attacks to creatures behind it.
Its space is impassible terrain.
A creature can attempt to break and pass through the barrier, and must succeed on a DC 30 Strength check to do so. Passing through in this way counts as difficult terrain., and also breaks the wall, and ends the concentration of the caster.
When a creature succeeds a 30 strength check and enters the wall's area, the creature must make a DC constitution saving throw as the wall of air breaks. On a failed save, the creature takes 1d8 crushing damage. On a successful save, the creature takes half as much damage.