You brandish the weapon used in the spell’s casting and make a melee attack with it against one creature within 5 feet of you. On a 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.   This spell’s damage increases when you reach certain levels. At 5th level, the melee attack deals an extra 1d8 necrotic damage to the target on a hit, and the damage the target takes for making an attack or casting a spell increases to 2d8. Both damage rolls increase by 1d8 at 11th level (2d8 and 3d8) and again at 17th level (3d8 and 4d8).