Okay, I remember reading this book back in highschool and liking it but i can't for the life of me figure out what it was called or who it was by.

The story revolves around a large emerald (I think) called the empire stone. (I thought the book might be called the empire stone but that doesn't turn up any results that match the plot in my head.) The main character, an elf-like woman is on a quest to gather up the people or things mentioned in a poem in order to...do something. Save the world? *shrugs*

The first clue describes her companion, a cat-like woman. The next is some guy in a tavern, I think. Each person she gathers up knows something that leads to the solution of the next clue in the poem (I think they all turn out to be people.) In addidion to the ones mentioned, I believe the group also ends up including a theif and a queen and the group visits at some point caves and also possibly a maze.

I realise a lot of ths sounds horribly cliche and could describe any number of books but hopefully this will all be familiar for someone.

Any ideas?