An interesting discussion that came up recently in one of my games.
A Warlock is already wearing leather armor and has AC of 11 (no dex mod) and takes the Eldritch Invocation of Armor of Shadows giving him/her Mage Armor.
This spell gives them AC of 13, however; "the spell ends if the target dons armor..."
So the question being discussed:
1. Some take the side of that the spell ends because he/she is already wearing the leather armor assuming this is already "donning" armor.
2. Some take the literal " Don- This is the time it takes to put on armor". and say since he/she was already wearing the armor and not actually "donning" it during the spell time it does boost the AC to 13 as stated in the spell.
Just curious what the community's thoughts/house rules are, and would be?
I would as a DM rule #2 unless some situation caused the Warlock to doff their armor and if they "donned" it again during the spell time, the spell would end.
The intent is that you can not stack armor and that if you wear armor you can not use the spell.
I would go with #1 anything else is trying to twist wording to gain an advantage. If you allow your interpretation #2 then you have to read each and every rule with this same kind of rules loop hole view. It also removes the intent of the spell and the purpose of the getting into and out of armor restricions. Armor is not easy to wear even leather and padded versions and treating them like a t-shirt and sweat pants will ignore the point of the getting into and out of rules.
However it is your game so it is as always up to you at your table.
Even if you could wear light with mage armor on, you still only get to pick 1. There's a rule in the PHB... somewhere.
So...
11+Dex
or
13+Dex
mellored wrote:
Thanks for your input. One great thing is everyone has a good viewpoint and interpretation.
Drycanth wrote:
What Mellored said. When you have 2 or more armor sources, you pick one.
So even going with the lenient wordage of the spell (ie, saying "I'm not DONNING armor, I ALREADY have it on 
"), you get to choose between:
11+Dex (what your AC is according to your armor and AC rules
Or 13+Dex (what your AC is according to your spell)
In no way Mage Armor meant/implied to stack. Same goes for if you add some class abilities into that mix (like a Dragon Sorcerer's Scales or Monk's Unarmored Defenses)
Yeah, this is one of those NBD rulings where literal RAW is silly. I recommend not forcing your warlock to take off his leather armor, since there's practically no benefit (just obscure stuff like the Mage armor getting dispelled).
I don't get why there's any confusion here at all. Literally the first sentence in mage armor says:
"You touch a willing creature who isn't wearing armor..."
Armor of Shadows lets you cast mage armor at will, it doesn't give you an always-on mage armor. You still have to cast the spell, which means you still can't be wearing armor when you cast it on yourself, in addition to the fact that the spell ends when you don armor after casting it.