"I'm hungry. Can you direct me to someone who's happy? I would like that."
A Dementor only known as "Dan", he and his life partner "Becca" are Alpha Dementors. They are to other Dementors like wizards and witches are to Muggles. They run the Dementors of Azkaban, and are not easily disposed of by mere Patronus Charms (though they do hurt...a lot)
What an Alpha Dementor is, no one can say. Are they wizards and witches who became Dementors themselves? Are they the father and mother of all Dementors? Are they something less? Something more?
Nobody knows. All that matters is that they are dangerous...