Strength of Sacrifice

When a creature you can see hits another creature within 5 feet of you with an attack roll, you can take a Reaction to either:

Reduce the damage dealt to the target by 1d12 plus your Proficiency Bonus. You must be holding a Shield or a Simple or Martial weapon to use this Reaction.

or

Take the full amount of damage onto yourself but the shielded character gains 1d10 plus your proficiency bonus in temporary HP.