Deadly Doorway

Life has many doors, just as death holds many keys.
When you cast this spell, you touch a doorway, gate, window, or other construction that serves as an opening between two locations. You can speak a word, phrase, or describe an action or activity that must be performed to secure safe passage through the door. The first creature that does not perform this safeguard while passing through the doorway must succeed a Charisma saving throw or take 5d10 necrotic damage and be paralyzed until the start of their next turn. A creature slain by this damage instantly withers into dust, leaving all of their clothing and possessions behind.

At Higher Levels: When you cast this spell using a spell slot of 5th level or higher, the necrotic damage increases by 2d10 per spell slot level above 4th.