You conjure and install a spiked portcullis in an archway or doorway that you can see within range. When you cast the spell, or as a reaction when a creature walks through the doorway, you can allow the portcullis to drop. When the portcullis falls, each creature beneath the doorway must make a Dexterity saving throw. A target takes 2d12 piercing damage on a failed save, or half as much on a success.   If a target survives the initial damage, it is pushed to one side of the portcullis (determined at random). After the portcullis falls, it remains there until the spell ends. It has AC 15 and 30 hit points, and is immune to poison and psychic damage. If the portcullis is destroyed, the spell ends.