You brandish the weapon used in the spell's casting and make a melee weapon attack with it against a target you can see within the weapon's reach. On a hit, the target suffers the weapon attack's normal effects, as a vein of magical energy bursts out from the point of the strike, creating an illusory swarm of spectral butterflies, birds, or similar creatures that surround you until the end of your next turn. The first attack that targets you after then subtracts 1d4 from its attack roll. An attacker is immune to this effect if it doesn't rely on sight, as with blindsight, or can see through illusions, as with truesight.
This spell adds damage to the initial attack when you reach certain levels. At 5th level, the attack deals an extra 1d4 psychic damage to the target on a hit, which increases by 1d4 at 11th level (2d4). Additionally, the die rolled for the disruption caused by the illusion increases by one step at 5th level (d6), and 11th level (d8).