A Thestral is a breed of winged horses with a skeletal body, face with reptilian features, and wide, leathery wings that resemble a bat's. They are very rare, and are considered dangerous by the Ministry of Magic.
A dog collar is a piece of material put around the neck of a dog. A collar may be used for control, identification, fashion, or other purposes. Identification tags and medical information are often placed on dog collars. Collars are also useful for controlling a dog manually, as they provide a handle for grabbing.
The martingale collar is also known as a limited-slip collar. This collar is designed for dogs with narrow heads such as Greyhounds and other sighthounds (such as the Afghan hound, Saluki, and whippet). It is also useful for a dog of any breed who is adept at slipping out of his collar.