Vengeful Blade

You brandish the weapon used in the spell's casting and
make a melee spell attack with it. On hit, the target suffers the weapon attack's normal effects and then radiates a dark aura of energy until the start of your next turn. If the target makes an attack or casts a spell
before then, the target takes 1D8 necrotic damage and
the spell ends.

At 5th level, the melee attack deals an extra 1D8 necrotic damage to the target on hit, and the damage the target takes for making an attack or casting a sp