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.
<span>Puck is a powerful supernatural creature, capable of circling the globe in 40 minutes or morphing unsuspecting mortals in a deep fog. Also known as Robin Good fellow, Puck would have been familiar to a sixteenth-century English audience, who would have recognized him as a common household spirit. But he's also a "puck," an elf or goblin that enjoys playing practical jokes on mortals. Although he is more mischievous than malevolent, Puck reminds us that the fairy world is not all goodness and generosity.</span>