Ironward crystal and mithril armor?

[ksbsnowowl]

In addition to that FAQ, Races of Wild shows various Mithral armors as simply one category lighter than the usual version. I mean, Mithral Breastplate is categorized as a light armor in that book.

I believe RAI is that mithral and similar special materials actually change the category of armors.

Hmmm... that might throw a kink into his plans.

Regardless, I may end up allowing it anyway, because it's not overpowered, and it's one of the two "freebies" that he wants.*

*Due to the nature of my campaign world, there is not a lot of opportunities to buy or upgrade equipment; they mostly get what they plunder off of bodies. But I try to tailor the loot to things I think they'll like, and I'm letting them choose two items they want that they will come upon at some point in their travels. Of course, the people they have to take them from will be using them effectively, but there it is.

 

[StreamOfTheSky]

Most GMs I have played with have ruled it as 'whatever is is most advantageous to the character'.

This. Mithral doesn' say it becomes one category lighter, it only counts as such for movement and other limitations. In other words, it only counts as lighter when it's beneficial.