Creature Codex Pocket Edition: 5th Edition - Rules of Play says:
Whether you need scuttling dungeon denizens, alien horrors, or sentient avatars of the World Tree, the Creature Codex Pocket Edition has you covered! More than 400 new foes for your 5th Edition game—everything from acid ants and grave behemoths to void giants and zombie lords. All in a convenient, portable size!