When you cast this spell, you protect a doorway, archway, gate or portal that later unleashes a magical effect on the first creature other than the caster that passes through.  A creature takes 1d10 lightning damage on a failed Dexterity saving throw.  Once triggered or at the end of its duration, the spell is dispelled.

The protection is nearly invisible and requires a successful Intelligence (Investigation or Arcana) check against your spell save DC to be found.

The spell’s damage increases by 1d10 when you reach 5th level (2d10), 11th level (3d10), and 17th level (4d10).