True Privacy

If you believe someone is using a divination spell targeting you (Detect Thoughts, Scrying, etc.)  then you can as a reaction cast this spell.    If no one is using one, your spell slot is wasted and nothing happens.  If someone is using a divination spell on you then they are in for a nasty surprise.

The unwanted spy is subject to a horrifying illusion that, like a dream, prevents them from looking away.  They must immediately make a Wisdom save or "True Privacy" establishes a psychic link which continues even if the spy cancels their divination spell.  If they fail their save, they immediately take 3d10 psychic damage and the spell continues for the duration.   If the spy makes their save, their own Divination spell ends and they only take half damage.

At the beginning of the spy's round, they must make another Wisdom save.  If they fail their save, they take 3d10 of psychic damage and "True Privacy" continues for another round.  They are also at disadvantage for every attack or ability check they make that round.   Saves are unaffected.   If they make their Wisdom Save they take half damage,  their divination spell ends, True Privacy ends and they are no longer at disadvantage.

In addition to making a save, the following methods will end this spell earlier:

1) If the caster of True Privacy fails a required concentration check, or otherwise stops concentrating.   Note, if the divination spell is still active, you can re-cast True Privacy.

2) A Dispel Magic, Remove Curse or similar effects used on either the spy or the caster of True Privacy.  This method will also end the Divination spell cast by the spy.

3) Either party Teleports or uses similar effects.  Note, if the divination spell is still active, you can re-cast True Privacy.