From publisher blurb:
The world's most famous fantasy role-playing game has a huge monster book, but many creatures we loved in prior editions were overlooked. The 5e Fiendopedia brings some of these back and updates them for the 5th edition rules.
This PDF includes 5 creatures: Dragon Horse, Dragonne, Phoenix, Sea Serpent, and Thunderbird
Each creature gets a full-color image, 5th edition statistics & abilities, and background/ecology information.