Dragon Scale

True dragons are a rare sight in the familiar lands and their scales can repel most weapons save for siege weaponry. Dragon scales get denser and sturdier the older the dragon gets; elder dragons that can no longer fly produce the most protective scales. Younger dragon scales are lighter and smaller, making them especially useful for flexible scalemail.

Beowulf has dragon scales underneath his armor, rotted and decayed, the scales having signs of the erasure rot that's somehow frozen in stasis.