High Rhulain is a novel by Brian Jacques, the eighteenth in the Redwall series. It will be published in 2005.

According to a description from Redwall.org :

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

Green Isle is home to the otterclans, but they are beset by dangers from Wildcat chieftain Riggu Fellis and his catguard 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!