[RPG] How do the Faerie Fire and Mirror Image spells interact

dnd-5espells

During a discussion on how mirror image interacts with area of effect spells, and particularly with magic missile, the question arose about how faerie fire interacts with mirror image. This is related to the general question of how mirror image interacts with spells that don't have an attack roll but is more specific.

The faerie fire spell description states:

Each object in a 20-foot cube within range is outlined in blue, green,
or violet light (your choice). Any creature in the area when the spell
is cast is also outlined in light if it fails a Dexterity saving
throw. For the duration, objects and affected creatures shed dim light
in a 10-foot radius.

Any attack roll against an affected creature or object has advantage
if the attacker can see it, and the affected creature or object can't
benefit from being invisible.

The description of mirror image says:

Three illusory duplicates of yourself appear in your space. Until the
spell ends, the duplicates move with you and mimic your actions,
shifting position so it's impossible to track which image is real. You
can use your action to dismiss the illusory duplicates.

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.

If you have three duplicates, you must roll a 6 or higher to change
the attack's target to a duplicate. With two duplicates, you must roll
an 8 or higher. With one duplicate, you must roll an 11 or higher.

A duplicate's AC equals 10 + your Dexterity modifier. If an attack
hits a duplicate, the duplicate is destroyed. A duplicate can be
destroyed only by an attack that hits it. It ignores all other damage
and effects. The spell ends when all three duplicates are destroyed.

Does faerie fire only light up the creature who cast mirror image, or do all of the illusory duplicates also get outlined/lit up by faerie fire?

Our guess was that faerie fire lights up all of the images, but since faerie fire is working like an AoE spell, and AoE spells aren't fooled by the images (fireball, etc), perhaps we misunderstood how these two spells interact.

Best Answer

I would rule that the original and the duplicates all have the effect of faerie fire visible. Faerie fire would outline all the duplicates and give advantage on attack rolls regardless. However while the spell does say

A duplicate can be destroyed only by an attack that hits it. It ignores all other damage and effects.

Mirror Image also says

Until the spell ends, the duplicates move with you and mimic your actions, shifting position so it's impossible to track which image is real.

I think that the duplicates would not be affected by faerie fire directly BUT seeing as the original is affected, they would alter their appearance to match that of the original thus conferring advantage to attacks made on them as the advantage is a result of faerie fire's outline making it easy to see the affected creature. (Otherwise why would the spell have to specify "if the attacker can see it"?)