When the Adamant Armor is equipped, then deequiped on any member of the party, the character becomes weak against every basic elemental (Fire, Ice, Lightning) unless there are other elemental protection available.
It seems that there is a bit(s) that is forgotten to be turned off when the Adamant Armor is deequipped, and the characters end up being severly weakened.
You can also transfer this to a new game after resetting the game and the character that was equipped with the Adamant Armor previously will be weak.
I'm not sure if this applies to FF4A though.
This does not apply to the Glass Helmet since the Immune attribute does not even work with this piece of equipment.
If someone is willing, please release a patch fixing this behavior.
Edit: It is worth pointing out that it affects FF2USHT's Cursed Ring as well.
Topic: FF2/4/4ET Immune attribute/Adamant Armor Bug (Read 2640 times)