Hunters' Quest (book 2 in the Hunters of Reloria series)

Peaceful Reloria is under siege by scaly Vergai invaders by portal who have captured the Elven Jewel which creates their protective forcefield. These Vergai live across the western sea, and have fled with the elven princess.
Halfling friends, Randir and Fendi and their bond-fairies are members of a group of brave hunters on a quest to recover the stolen Elven Jewel. They must search for a mage who can make a portal to rescue the princess. They thought they knew what the quest would entail, but with an unexpected member and new enemies, not everything goes the way they had planned.
Their journey takes them to strange new places including the centaur lands, the gnomish inventors, the Great Elven Heart and the home of the dragons.
This unlikely group of men, a dragon, dwarves, halflings, fairies and an elf are known as the Hunters of Reloria.