Aegis of the Weak

3rd-level necromancy
Casting time: 1 bonus action
Range: 30 feet
Target: A creature within range
Components: V S
Duration: Concentration, up to 1 minute
Classes: Warlock, Wizard, Sorcerer
Subclasses: --

You gesture to a creature within range and link your life-force to theirs. Until the spell ends, if the target's hit points would be reduced to 0 from damage the casater takes that damage instead.