Any material, but most commonly stone and steal, will transform into a molten, lethal bubbling wave of lava once the spelled armour comes into contact with it - and if mastered, it's said the Magus could even summon a true volcano.
One of Acre's very first apparentices, who's lineage lives on in the Vermillion Tower to this day, took the Paragon's tell-tale forging techniques one step further - and at Acre's death, it's said that Ismat melted the founder's anvil in a fit of pure hot rage after her daughter was slayed during one of Acre's many battles.
Strictly military, strictly Vermillion, strictly Meketh-family approved. Common with Meketh-descendant soldiers and officers. However, a precious few pieces have been stolen from the original armour-set; a battle tiara and bracers, among other things. These are sold and traded for extensive prices on the black market, and can show up anywhere.