Essence of Stone

Eight Gates appeared on Earth. For some time, humanity believed it had made contact with an alien civilization. Then the excitement faded, and the Gates became part of everyday life.

When a new Gate opens near his mountain village, Mac witnesses something impossible: a young man stepping out of it. His name is Art. He comes from another world.

Mac soon discovers that his world is only one branch of a vast Delta of parallel Variants connected by the Gates—and that rare travelers called Striders cross between them in search of Quintessence, a mysterious force that powers civilizations and may reveal the true nature of reality.