Since the ancient times, tens of thousands of territories cascade the starry universe, and the galaxy spans across the sky. In a world where tamed beasts exist throughout the vast and starry universe, innumerable clans are contending for hegemony. “Planet travelers", including Beast Tamers and various kinds of tamed beasts—plantal beasts, walking beasts, mechanical beasts and elemental beasts—traverse the planets in this galaxy. Bai Ye, a teenager who lives on Obsidian Planet, embarks on a beast-taming journey after his parents left him and his sister behind, along with a secret possession much coveted by others. He eventually travels out of Obsidian Planet to other places in the galaxy, signing soul contracts with tamed beasts from the mysterious tomb in his dream along the way. As he strives to become stronger in an initial pursuit for self-defence, Bai Ye incidentally takes on the path to invincibility.