Welcome to Theros

They were alone on the glassy blue ocean. A waterfall stretched endlessly along the horizon line. The water at the edge of the world was like a placid pond, as if enjoying a last few seconds of existence before cascading over the edge in a raging torrent of white-capped water.
Directly in front of them was Kruphix's Tree. Two enormous trunks were separate at the base, but they arched toward each other and joined at the top in a single leafy crown. Stars glittered beyond the waterfall, but the background was milky violet with tinges of deep blue. The sea-water that plummeted over the edge disappeared into the abyss of the stars.
They had reached the edge of the world.

- Henna Helland, Godsend

The caprice of the gods. The destiny of heroes. Great journeys into monster-infested wilds, and mythic odysseys to the edge of the world and back. These elements of adventure fill the realms of Theros, whose roots lie in the myths of ancient Greece, tales dominated by gods, heroes, and monsters.
This book is your guide to Theros, its gods, its peoples and their cities (or poleis), its threats, and its tales. It also guides you through creating characters destined to be legends and adventures born of this mythic setting.

Chapter 1 covers the heroes of Theros: the races, class options, and backgrounds you'll need to make a character. It also introduces supernatural gifts available to starting characters - features that set Theros's adventurers apart as true heroes.
Chapter 2 introduces the gods of Theros, a squabbling pantheon of arrogant and powerful beings who view mortals as pawns in their strategic games. It also provides rules and guidelines for characters who serve as champions of the gods, including divine benefits they can gain as rewards for their piety.
Chapter 3 turns to the mortal world, the lands in which the epic adventures of Theros unfold. It covers the three city-states of humanity, the wild lands of leonin and minotaurs, the great forests and wide plains where satyrs revel and centaurs roam, and the seas where tritons dwell and titanic monsters lurk. It also offers glimpses into the divine realm of Nyx amd the dismal realms of the Underworld.
Chapter 4 builds on the guidelines in the Dungeon Master Guide, highlighting adventures set in Theros. Maintaining a focus on the gods, it presents omens that might launch heroes on the road to adventure, details hundreds of plot hooks, including maps of potential adventure locations, and presents a short introductory adventure you can use to launch your campaign.
Chapter 5 details treasures of Theros, including the artifacts of the gods, the magical inventions of renowned artisans, and various other devices infused with the magic of the world.
Finally, chapter 6 presents numerous inhabitants of Theros. An exploration of familiar beasts from the Monster Manual and other sources - creatures with their roots in Greek mythology - details their place and unique characteristics in the lands of Theros. Several of Theros's most notorious creatures, foes as legendary as the world's most renowned heroes, are also presented as mythic monsters, terrors designed to test even the gods' mightiest champions.