Armor, Red Iron (5e Equipment)
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Armor (any medium or heavy armor made of metal), uncommon, rare (+1), very rare (+2), or legendary (+3)
Red iron, also known as red steel, is a special type of steel with a red, pinkish, or purplish coloration. Armor made of this material is completely immune to all forms of rust and corrosion, and heavily resistant to destruction. If armor made of red iron is subjected to an effect that would destroy any ordinary object outright, such as a disintegrate spell, roll a d20. On a roll of 9 or lower the armor is damaged, taking a permanent and cumulative -1 penalty to the AC it offers. The armor is only destroyed if the penalty reduces its AC to 10.
Because of red iron's slight anti-magical properties, you are unable to cast spells while wearing the armor. In addition, objects made of red iron are unable to hold magical imbuements or bear curses.
The uncommon red iron version of a set of armor costs 100 gp more than the normal version.
Armor made of red iron that has been refined to a high degree exhibits strong anti-magical properties, represented by a bonus ranging from +1 to +3. While wearing this armor, you gain that bonus to saving throws made against magical effects. In addition, the armor reduces all damage from magical weapons and effects by an amount equal to its bonus.
The armor also gains the bonus to the d20 roll made to determine whether or not it is damaged. When refined red iron armor is damaged, the penalty is first deducted from its anti-magic bonus, then the AC it offers.