Probably one of the rarest semi naturally occurring elements, promethium is radioactive and decays generally into neodymium. It’s mostly used in batteries and luminous paint.
Hedgehogs are actually omnivorous, despite often being thought of as chiefly in the now abandoned Insectivora. They will eat fruit, berries, ants, slugs, eggs, snakes, snails and pretty much anything small enough. Their spines make them a hard to hunt animal and protect them from their chief predators, owls, foxes, dog and domestic cats. Their defense mechanism is what made me tie them to promethium.
Samarium is another “common” rare earth metal, having a occurrence of about 40th in The rarity of metals in the Earths crust. A myth about Samarium is it named after the ancient civilization of Samaria, which is untrue. It is in fact the first element to have been named after a person Colonel Vassili Samarsky-Bykhovets. It’s a pretty useful rare earth element, being used in batteries, superconducting magnets, and quantum computing. It will form alloys with most other elements, these alloys are how it is usually used.
Badgers are also omnivores, and often can be surprisingly vicious for their size. They live in family groups that often hunt and eat together. They can be inquisitive but very shy creatures, but have been known to team up with foxes and coyotes for hunts, though in desperate times they will hunt each other! Samarium is tied to badger as they are both sharing but somewhat shy and difficult at times.