Doomwyte

Doomwyte is a fantasy book written by Brian Jacques in 2008. It is the 20th book in the Redwall series.
Plot.
A young mouse named Bisky who lives at Redwall Abbey figures out riddles with his friends to find four beautiful jewels that had been hidden in Redwall a long time ago. But at the same time an evil raven is trying to find the gems too, because they had belonged to his kingdom a long time ago.