Leprechauns are one of the more human-like creatures, but they've never requested "being" status.
They tend to like Muggle attention, which is why they feature so often in Muggle stories.
They enjoy passing out gold pieces which disappear after a few hours…and that makes them laugh and laugh and laugh. (Jerks.)
(Harry Potter book shout out: In Harry Potter and the Goblet of Fire, the leprechauns show up at the Quidditch World Cup to support the Irish team and toss out a bunch of gold coins…which later, of course, disappear.)
The Lethifold looks like a black cloak or a shadow. It usually attacks at night and creeps along the ground.
While its victim is sleeping, the creature will slip over the person's face and suffocate them and then digest them right then and there. Hello, new nightmares!
It's tough to know how many people have been attacked by Lethifolds since the creature leaves no trace of its victim.
This sea creature has a venom sac that releases poison when it's threatened.
Merpeople use these as weapons and wizards have used the poisons in some potions, too.