Warlock Guide to the Planes

From the introduction: Listen, friend. Clearly you ain’t got no idea which way the Ever River flows, so let me clue you in, right? The world you came from—its moons and stars and so forth—that’s just one plane in an endless multiverse of planes. Each one its own sphere suspended in the branches of Yggdrasil, the World Tree, and touched by the twisting course of the Ever River. The planes ain’t worlds like whatever benighted rock you stepped off. These are infinite realities, dimensions of cosmological existence. You’ve got your hells and heavens sure. But you’ve also got marketplace worlds and endless forests. You’ve got your unending battlefields and your gloaming fields of undeath. And surrounding ’em all is the Yawning Void where elder things sleep. I know not why you came, but out here, there’s enough adventure, treasure, mystery, and peril to satisfy any band of would-be heroes. So open your eyes to a larger cosmos, but watch your step, friend. For among the planes, delights and dangers await in equal measure.