Prerequisite: 5th level
As an action, you can designate one friendly creature you can see as your sidekick. While you and your sidekick are within 10 feet of one another, each of you can use a reaction to take half of an instance of damage dealt to the other. Once you choose a sidekick, you can't choose a new one until you finish a long rest, and you can only have one sidekick at a time.