Eternal winter

You create a wall of tough, pliable, tangled brush bristling with needle-sharp thorns. The wall appears within range on a solid surface and lasts for the duration. You choose to make the wall up to 60 feet long, 10 feet high, and 5 feet thick or a circle that has a 20-foot diameter and is up to 20 feet high and 5 feet thick. The wall blocks line of sight. When the wall appears, each creature within its area must make a dexterity saving throw. On a failed save, a creature takes 7d8 piercing damage, or half as much damage on a successful save. A creature can move through the wall, albeit slowly and painfully. For every 1 foot a creature moves through the wall, it must spend 4 feet of movement. Furthermore, the first time a creature enters the wall on a turn or ends its turn there, the creature must make a dexterity saving throw. It takes 7d8 slashing damage on a failed save, or half as much damage on a successful one.