Added tag "knowledge".
The answer is:
The images are of the following creatures from the Harry Potter / Fantastic Beasts world: Murtlap, Occamy, Grindylow, Diricawl, Mooncalf, Graphorn, Hippogriff, Niffler, Centaur, Bowtruckle
For each image, you count the number of creatures in the image, and take the nth letter from the name of the creature: 1 murtlap, 4 occamy, 1 grindylow, 2 diricawl, 5 mooncalf, 2 graphorn, 1 hippogriff, 2 niffler, 3 centaur, 2 bowtruckle.
These letters spell out magic rhino. This is a reference to the Erumpent, which is a magical rhino from Fantastic Beasts (pictured above).