When you hit a creature with a melee weapon Attack, you can expend one spell slot to deal radiant damage to the target, in addition to the weapon's damage. The extra damage is 2d8 for a 1st-level spell slot, plus 1d8 for each Spell Level higher than 1st, to a maximum of 5d8. The damage increases by 1d8 if the target is an Undead or a fiend.