High Rhulain, Published in 2005 by Brian Jacques, Philomel Books

Young Tiria Wildlough is and ottermaid touched by the paw of destiny. Her epic adventures take her on a journey from Redwall Abbey across the Great Western Sea, to the mysterious Green Isle. There she must fulfill and ancient prophecy and gain her inheritance.

Green Isle is home to the otterclans, but they are beset by dangers from the wildcat chieftain Riggu Felis and his catgaurd slave masters.  Aided by two birds and a platoon of Long Patrol Hares, Tiria joins forces with the outlaw leader of the otterclans in a battle that will test all their courage and skill.

In the true tradition of Redwall comes a new saga full of feasts and fighting, riddles and quests, and a heroine you're not likely to forget as she strives to become the chosen one--the High Rhulain!

This 18th book of the Redwall series, written by Brian Jacques, is one of the few books in which the main character (Tiria the otter)  finds out that she is a ruler, more precisely a queen, and even more precisely the High Rhulain, the queen of all otters on Green Isle, which is currently ruled by vicious wildcats. It might be the only one, excluding books like Lord Brocktree, in which a badger receives the lordship of Salamandastron when his successor dies. This book is also one of the several books in which the good creatures take a long voyage. I like how Brian added common things into this part of book., like seasickness. It really improves the plot. This also is a great Redwall book.