Mithryl is a very rare silvery, glistening metal that is lighter than steel but just as hard.
When worked like steel, it becomes a wonderful material from which to create armor, and is occasionally used for other items as well. Most mithryl armors are one category lighter than normal for purposes of movement and other limitations. Heavy armors are treated as medium, and medium armors are treated as light, but light armors are still treated as light. This decrease does not apply to proficiency in wearing the armor. A character wearing mithryl full plate must be proficient in wearing heavy armor to avoid adding the armor's check penalty to all his attack rolls and skill checks that involve moving. Spell failure chances for armors and shields made from mithryl are decreased by 10%, maximum Dexterity bonuses are increased by 2, and armor check penalties are decreased by 3 (to a minimum of 0).
Items not primarily of metal are not meaningfully affected by being partially made of mithryl. (A longsword can be a mithral weapon, while a quarterstaff cannot.) Mithryl weapons count as silver for the purpose of overcoming damage reduction.
Section 15 -- Copyright Notice Edit
Pathfinder Roleplaying Game Ultimate Equipment. © 2012 Paizo Publishing, LLC; Authors: Dennis Baker, Jesse Benner, Benjamin Bruck, Ross Byers, Brian J. Cortijo, Ryan Costello, Mike Ferguson, Matt Goetz, Jim Groves, Tracy Hurley, Matt James, Jonathan H. Keith, Michael Kenway, Hal MacLean, Jason Nelson, Tork Shaw, Owen KC Stephens, and Russ Taylor.