Captain's Smite

As you hit the target, it takes an extra 2d6 Cold damage from the attack. At the start of each of its turns until the spell ends, the target takes 1d6 Fire damage and then makes a Wisdom saving throw. After three failed saves, the creature starts to roll the saving throw with advantage.

Using a Higher-Level Spell Slot. All the damage increases by 1d6 for each spell slot level above 1.