Butterfly Blade

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 weapons 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 illusionary swarm of butterflies, birds, or similar creatures that surround you. The first melee attack that targets you before the spell ends subtracts 1d4 from it's 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 does an extra 1d8 psychic damage to the target on a hit, which increases by 1d8 at 11th level (2d8) and 17th level (3d8).