You summon a shadow as described in the Monster Manual and it instantly merges with your own shadow. Only creatures with truesight are aware of the two merged shadows. Each time you are hit by an attack, the shadow takes the damage instead of you. If you are hit by a melee attack, the shadow makes an attack of opportunity to the target. This shadow cannot take any action. The shadow disappears when it is reduced to 0 hit points or the spell ends. You can dismiss the spell on your turn as a bonus action.