The target hit by the strike takes an extra 2d6 Radiant damage from the attack. If the spell kills its target the caster makes a DC13 constitution check, on a success a blessed wisp* that lasts for 1d4 turns is summoned. 

Using a Higher-Level Spell Slot. The damage increases by 1d6 for each spell slot level above 2.

*For Blessed Wisps Use the Will-o'wisp stat block with the following amendments:
-Cannot use consume life
-Is immune to necrotic damage