Xanathar's Guide to Everything includes this fun magical armor variant, Cast-Off Armor, which can be doffed in a single action (see XGE p136):
You can doff this armor as an action.
This is generally simple to understand and use, until we get to Warforged (from Eberron: Rising from the Last War). Warforged have the interesting racial ability to integrate armor into themselves, as shown below:
Integrated Protection. Your body has built-in defensive layers, which can be enhanced with armor:
- You gain a +1 bonus to Armor Class.
- You can don only armor with which you have proficiency. To don armor, you must incorporate it into your body over the course of 1 hour, during which you remain in contact with the armor. To doff armor, you must spend 1 hour removing it. You can rest while donning or doffing armor in this way.
- While you live, your armor can't be removed from your body against your will.
Assuming that a Warforged is proficient with a piece of Cast-Off Armor, are they able to use the Cast-Off ability to doff the armor in one action, thanks to it being a magical property of the armor? Or does their Integrated Protection render the magic of the Cast-Off Armor effectively moot?