Lioness Rampant (Song of the Lioness)

is book #4 of the Song of the Lioness quartet.
==Book Description==
At last, Alanna of Trebond has become the first female knight errant in Tortall. She sets out on an impossible quest to find the Dominion Jewel, a legendary gem that, in the right hands, has limitless power for good. But while she searches for the one thing that can save her war-torn country, her nemesis returns from the dead and begins to wreak havoc. Only Alanna has the power to prevent Tortall's utter destruction ...
In this final verse of the Song of the Lioness quartet, Alanna grows from heroine into legend. 
(Description from paperbackswap.com)