Dorian's Devastating Display

You create a magical canvas that is up to 20 feet long, 10 feet high and 3 inches thick.  it must be at least 1 foot wide, long, and 1 inch thick  It needs to be anchored to a wall, ceiling or floor.  To creatures you designate or to creatures who speak a password of your choice within 120 feet of the canvas, the painting looks like a normal painting.  Otherwise, the painting appears to be a painting of something beyond the mind's ability to imagine.  If a creature comes within 60 feet of this canvas and can see it without being exempt from its effects, it must pass an Intelligence Saving throw.  On a fail, the creature's mind is bombarded with images that intensely disturb and overwhelm them, causing 10d12 psychic damage and causing them to be stunned for 10 minutes, or until they take damage or are shaken awake.  On a success the creature takes half as much damage and is not stunned.  After a creature is affected by this ability, they lose memory of the painting and it becomes invisible to them for 1 hour, rendering it harmless for that time to them.  On a successful DC 23 History check, they may be able to force out  a memory of the painting in order to remember it.  When a creature who failed this save survives the psychic blast, the caster of the spell knows the creature's exact location for 24 hours.