|Source||natural - Limbo|
This russet colored metal is only found naturally in the Limbo system. Berusk is a metal with the properties of iron. It is tainted from the Dawn Era, when it was used in great fortifications, the building of iron golems, and in armor. The battles of Limbo's worlds saw opposing sides use shape-changing magic to no end. This affected living bodies, animated ones, and structures. To counter this, great quantities of iron ore were put in huge cauldrons, then infused with Negative Entropy.
Armor made of this metal provides +2 on saves vs Will attacks and +5 on saves that force a change to the wearer's body; like from a polymorph spell or the shape changing of a lycanthrope. It can also be used in reinforcing structures, with berusk re-bars affording the same protections against spells like rock to mud.
In some areas of the realm, known shape-changers, are either forced to wear this in populated areas, or do so to avoid causing problems.