Adamantine (Rune)

This rune is written in Dwarvish and can be transferred to any medium or heavy armor, but not hide.

While wearing the armor that bears this rune, you can activate the rune as a bonus action to magically reinforce the armor with adamantine for 10 minutes. For the duration, the armor grants you a +1 bonus to AC, and any critical hit against you becomes a normal hit.

Once activated, roll a d6. On a roll of 3 or lower, this rune can’t be used again until the next dawn.