Ceratimus is a ceramic-based material equivalent in strength to hard metal. Once a closely guarded secret, today it is manufactured by the Pyrmidian Ghouls, various githyanki groups, and Xi Institute.
Ceratimus is unaffected by electricity. When used to make half-plate or better armor, it provides energy resistance - electricity 5 to the wearer. It also weighs half that of normal armor. Ceratimus can only be used to make armor types suitable for ceramic molds; shields, breastplates, half-plate, full plate. Armor made of this material is treated as one category lower, so full plate is normally heavy armor, but a ceratimus suit is treated as medium armor. This reduced category only applies to arcane spell failure, armor check penalty and movement. It does not apply to maximum dexterity bonus because it is still a bulky armor. The same adjustments apply to a breastplate, which would fall into the light armors.