Elven Star (Death Gate Cycle #2) by Margaret Weis, Tracy Hickman

On steamy Pryan, never-ending sunlight and plentiful rain have created a jungle so vast that humans and elves dwell high in the trees and only dwarves live anywhere near the ground. From the treetops the aristocratic elves sell weapons to the other races, whose incessant warfare sends a steady steam of profits and essential resources skyward. Now, generations of dissent and race hatred will not heal -- not even under the threat of annihilation at the hands of legendary Titans. Armed with little more than their wits and prophecy, an elf, a human, and a dwarf must unite to try to save the world from destruction.

On steamy Pryan, never-ending sunlight and plentiful rain have created a jungle so vast that humans and elves dwell high in the trees and only dwarves live anywhere near the ground. From the treetops the aristocratic elves sell weapons to the other races, whose incessant warfare sends a steady steam of profits and essential resources skyward. Now, generations of dissent and race hatred will not heal -- not even under the threat of annihilation at the hands of legendary Titans. Armed with little more than their wits and prophecy, an elf, a human, and a dwarf must unite to try to save the world from destruction.

On steamy Pryan. Realm of Fire, never-ending sunlight and plentiful rain have created a jungle so vast that humans and elves dwell high in the trees and only dwarves live anywhere near the ground. From the treetops the aristocratic elves sell weapons to the other races, whose incessant warfare sends a steady stream of profits and essential resources skyward. Now generations of dissent and race hatred will not heal--not even under the threat of annihilation at the hands of the legendary tytans. Armed with little more than their wits and a prophecy, an elf, a human, and a dwarf must unite to try to save the world from destruction.

THE DEATH GATE CYCLE
Ages ago. sorcerers of unmatched power sundered a world into four realms--sky. fire, stone. and water--then vanished. Over time, magicians learned to work spells only in their own realms and forgot the others. Now only the few who have survived the Labyrinth and crossed the Death Gate know of the presence of all four realms--and even they have yet to unravel the mysteries of their severed world....