From publisher blurb:
This one-of-a-kind bestiary brings you never-before-seen creatures as well as their swarm equivalents. But these aren't just run-of-the-mill swarms! Each creature has been given a minimum of two pages to help you understand their lore, their habits, their tactics, and why they swarm. Many of the swarms feature differences from their base creatures to keep your party guessing. Plus, we've got tons of bonus material and instructions on how to make swarms that are balanced for fifth edition.
This book includes:
Over 70 brand new creatures and their associated swarms!
All the creatures swarm, have swarm-like abilities, or summon and command swarms
Creatures and swarms of all sizes, including gargantuan!
Creatures and swarms for all environments!
Over 140 stat blocks ranging from CR 0 to 30, including new mechanics, traits, and actions!
Over 150 adventure hooks to help you integrate the creatures into your campaign!
4 new demiplanes to explore, including a demiplane made from books!
Bonus material including magic items, lairs, variants, templates, diseases, factions, and more!
Instructions on how to create swarms that are balanced for fifth edition!
Tips and tools to enhance the swarms you create, including making symbiotic swarm hosts!
50 wild effects!