The used rhetorical device is Hyperbole.
Saying that something is a billion times better is hyperbole because it is not really that much better, you would just be over exaggerating.
Explanation:
allegory
Why do the Terrible Thing take away animals one at a time?When the terrible things first came for the creatures with feathers on their backs, the animals who didn’t have feathers showed the terrible things that they they had none, while the birds tried to fly away. When the terrible things caught the birds and took them away, the other creatures were thankful that the terrible things did not take them, and they didn’t really care that the birds were taken.
