From the publisher:
Singed, bloodied, and battered, the adventurers stare past the body of the fallen dragon, eager to begin ransacking its horde of treasure. Already, their eyes gleam, and their minds dance with the possibilities: piles of coins, heady thoughts of eldritch weapons, and the promise of a rune-encrusted tome. Unnoticed among these riches is a battered, once gleaming key, dangling by a leather thong from the hilt of a sword.
The key stands out because it is so common an item amongst such uncommon wealth. It was probably the property of some adventure with less luck than the now-victorious party, and opens nothing more interesting than an old strongbox; certainly nothing of merit when compared to the wealth sitting before them. So it will simply hang there, or perhaps be tossed into a pouch, with no one ever realizing that this innocuous key is the vessel for considerable magical power.
It is the very plainness and strong symbolic properties of keys that mark them as excellent choices for enchantments involving locks, passage and hidden entries; as well as less tangible forms of opening and opportunity. This volume presents a selection of magical keys to help unlock new worlds of adventures, as well as rules for the duplication of normal keys.