A guard scroll is an item that is used to fortify your armor and shields. It mostly given as quest rewards. Until the fifth level it has a perfect durability but later it has a chance of failure. If the procedure fails your item will be destroyed.
level 1-3: +3%
level 4-6: +5%
level 7-9: +7%
level 10: +10%
When it reaches lvl 6, 8 and 10 it will receive a randomly chosen extra ability.