Fluffy is based on Cerberus the 3 headed dog from Greek Mythology that guarded the underworld to stop people escaping
Surely Fluffy, the 3-headed giant dog, would qualify.
Dobby.
Owls
Buckbeak is a hippogriff (A magical half-horse half-eagle creature).
Buckbeak is a creature that Hagrid has in a magical creatures lesson in the third harry potter movie. To most, it would seem it is a mixture of a bird, and a horse. the proper name of this creature is a hypogriff.
Fluffy was in the first Harry Potter... Harry Potter and the Sorcerer's Stone.
Surely Fluffy, the 3-headed giant dog, would qualify.
Fluffy.
No, Harry Potter is an original idea that uses mythological creatures and other fantasy characters.
Pigmy puffs.
Sure.
Dobby.
The creatures in Harry Potter that drain people of their souls are called dementors.
Harry and Fawkes defeated a Basilisk.
A Phoenix is a mythological creature with an 'x' in its name. If you have ever seen 'Harry Potter' - Fawks is a Phoenix. They are normally golden/reddish birds that possess unusual abilities. The legend is - as most are (see Vampires) - ever-changing.
On eBay it varies from $2.99 to $49.88
It has three heads (if you mean Fluffy).