This will be a small, but detailed guide on Beast Mastery.
A very important rule: If your beast dies, you die as well, and vice versa.
Tier 1: You are able to connect with one beast, and only one.
Tier 2: You are now able to connect with three beasts at a time, and you know have four minds instead of two.
Tier 3: You are now able to connect with five beasts and have grasped the ability to see through the eyes of your animal partners.
Tier 4: You are now able to connect even larger and more powerful creatures than before, but at the loss of a few of your other companions. These creatures are limited to 60 feet. And animals will either fear or respect you. You are now able to connect with seven beasts. (The 40 foot creature, will require you to give up the rest of your animal companions)
Tier 5: You are now at the pinnacle of Beast Mastery. Other races fear your pheromones, and your connection with the animals has now increased your physical attributes as well. (It depends on the creature/s you have.)
You can now connect with beasts massive enough to level a city. Your appearance is also altered to that more like a beast. (Does not apply to Beast Folk.) You are now able to connect with ten beasts. (The requirement for the Kaiju, are same as for the 40 foot creature.)