From the back of the book:
Someone in the misty, wooded, Mooonshae [sic] Isles needs hundreds of brand-new swords taken under guard from Sword Coast smiths to a certain place on the Isles.
The swords are needed so badly, and their safe arrival is considered so unlikely, that someone is willing to pay adventurers a lot of gold — someone fairly important.
Adventurers foolish enough to take assignments too good to be true (or merely desperate for coins) will soon find themselves embroiled in a dark and mysterious struggle against evil that will take them into sacred groves, crumbling castles, and through ancient magical gates to the halls of the High King -- and beyond.
This sourcebook contains background lore on the Moonshaes, a DM's delight of new monsters, magic items, and spells usable in any AD&D(r) campaign and enough adventure ideas to keep the most energetic player characters seeking their fortunes in the Mooonshaes [sic] for years to come!