I'm making a passive warlock tank. The idea being that I cast Armour of Agathys for the temporary hit points and the Mirror Image to keep me alive longer. It will be a solo NPC opponent for a 5/6 PC party.
Mirror Image makes 3 duplicate that are indistinguishable from me so I would assume they have the frost aura protecting them as well.
Is this correct? Would a PC making a melee attack against a mirror image take 5 frost damage?
No, they do not.
Armor of Agathys reads as follows (emphasis mine):
...if a creature hits you while you have these hit points, the creature takes 5 cold damage.
And mirror image:
Each time a creature targets you with an attack during the spell's duration, roll a d20 to determine whether the attack instead targets one of your duplicates
Mirror image makes illusory images of yourself, that move exactly like you do. They are not, however, actual duplicates of you, including active effects. Armor of Agathys only damages creatures that hit you, not you and any illusions of you.
The illusions do get the visual effect of Armor of Agathys, though.
