From the website:
Discover the truth about the great conflicts of the multiverse in this supplement for the world's greatest roleplaying game.
This tome is built on the writings of the renowned wizard from the world of Greyhawk, gathered over a lifetime of research, scholarship, and travel to other realms. In addition to Mordenkainen's musings on the endless wars of the multiverse, this record contains game statistics for dozens of monsters: new demons and devils, several varieties of elves and duergar, and a vast array of other creatures from throughout the planes of existence.
Included in Roll20’s complete adaptation of Mordenkainen's Tome of Foes:
New Monsters. Over 230 new monsters to drag & drop into your D&D 5e games. Each creature includes complete stats, one-click actions, beautiful tokens, and original artwork.
New Character Options. Explore deeper options for elves, dwarves, halflings, gnomes and tieflings. Uncover rules for playing as one of the gith in their magnificent 5th edition debut.
New Lore. Information on the Blood War - the endless fight between devils and demons. Easily search and share handouts on the devilish Lords of the Nine, the demonic Princes of the Abyss, the Raven Queen and her servants, and much more.
All entries are fully integrated into the Roll20 D&D 5th Edition Compendium and will unlock upon purchase and launch. This product is designed for use with the Roll20 Official 5E OGL Character Sheet.