At 3rd level, when you hit a creature with a melee weapon attack, you can expend a spell slot to deal radiant damage to the target and all other creatures within 5 feet of you, in addition to the weapon’s damage. A creature can make a Dexterity saving throw, taking half damage on a success. The extra damage is 2d6 for a 1st-level spell slot, plus 1d6 for each spell level higher than 1st.
A melee weapon attack can benefit from either your Crusader Strike or Divine Storm feature, but only one such effect can be applied to an attack.