Perhaps you create a new breed of Giant Beasts. This is by no way scientific. Just spit balling.
Choose any beast that isn't already a giant beast or swarm. Double that creature's hit points. You increase it's CR, AC, saving throws and DC for any abilities it has by 2. Increase its size to the next size category. Double the number of damage dice you roll for any attacks.
The numbers may be off, but this just gives a run down of what I'm thinking.
Choose any beast that isn't already a giant beast or swarm. Double that creature's hit points. You increase it's CR, AC, saving throws and DC for any abilities it has by 2. Increase its size to the next size category. Double the number of damage dice you roll for any attacks.
The numbers may be off, but this just gives a run down of what I'm thinking.