Short answers, pulled from the story.
James Wyatt and F. Wesley Schneider served as lead designers on the Mythic Odysseys of Theros book. James Wyatt began writing free PDF releases called Plane Shift in 2016 before moving to Magic: The Gathering in 2014.
The new sourcebook was officially announced on the 2nd of March 2020 but printing delays pushed the hardcover launch back to the 21st of July 2020. Wizards of the Coast originally scheduled the release for the 2nd of June 2020 before the COVID-19 pandemic caused further delays.
The supplement introduces two new playable races known as satyr and Leonin which are feline creatures from the Magic: The Gathering collectible card game. Three other races appear as reprints including centaur, minotaur, and Triton from previous sources like Guildmasters' Guide to Ravnica and Volo's Guide to Monsters.
Mythic Odyssey of Theros ranked seventh in Hardcover Nonfiction during the week ending the 25th of July 2020 with sales of 14,028 units recorded by Publishers Weekly. This performance occurred despite the book arriving when consumer attention was already fragmented across other releases.
James Wyatt described the development process as additive rather than subtractive because the Magic team creates illusions of worlds behind movie set facades while D&D players require actual buildings and spaces to explore those worlds. The team expanded existing world guides to flesh out details missing from the original card sets released in September 2013.