Hex

Until the spell ends, you deal an extra 1d6
necrotic damage to the target whenever you hit it
with an attack. Choose one ability, the target has disadvantage on ability checks made with that
ability.
If the target drops to 0 hit points before this spell
ends, you can use a bonus action on a subsequent
turn of yours to curse a new creature.
A remove curse cast on the target ends this
spell early.