Vengeful Blade (5.5e Patch)

You make one attack with the weapon used in the spell's casting. On a hit, the target suffers the weapon attack’s effects, and any damage from the weapon attack instead deals Necrotic damage in place of its regular type. The target is then cursed until the start of your next turn. If the target makes an attack or casts a spell before then, it takes 1d8 Necrotic damage, and the spell ends.

Cantrip Upgrade. The curse's damage increases by 1d8 when you reach levels 5 (2d8), 11 (3d8), and 17 (4d8)