Player's Guide Theros.

A number of powerful gods rule the world of Theros. Walled cities are threatened by squatters, minotaurs, hydras and other monsters. Heroes, strengthened by their dedication to the gods, come from all over the world to defeat these monsters. The Theros set tells the story of this world with new cards, including legendary divine creatures, powerful enchantments and brand new Planeswalkers!
Theros is the first set in the Theros Block and consists of 249 cards.

This Magic: the Gathering Player's Guide gives you a glimpse into the world of Theros. In addition, the Player's Guide is a complete encyclopedia of all cards from this set.

Note: the description is machine translated and might contain errors.