Divine Smite

Trigger (non-action):
You hit a creature with a melee attack.
Expend one spell slot to deal radiant damage
to the target, in addition to weapon damage.
The radiant damage is 2d8 for a 1st-level slot
+1d8 for each spell level above first (max
5d8). The damage incrases by 1d8 if the
target is an Undead or Fiend (max 6d8).