Dragons are found in the myths of many cultures, and appear in many different configurations. The name comes from the Greek "draconta" which means "to watch." Often, dragons are portrayed as guarding an object or a particular area.

In Western myths, dragons are generally dangerous carnivorous reptiles, and can be categorized by their appearance or habitat.

Native American Seneca myth tells of Gaasyendietha, a dragon that lives in the water but can shoot fire.

Dragons are the most evil of creatures, they are known as users and deceivers of man, they are liars and thefts, hence their hoards of treasure.

Dragons are even found in the Bible.

Rev 13:3 And I saw one of his heads as it were wounded to death; and his deadly wound was healed: and all the world wondered after the beast. Some Worship the "dragon" and the Beast. The "dragon" Gives Power to the Sea Beast for 3.5 Years.
Rev 13:4 And they worshipped the dragon which gave power unto the beast and they worshipped the beast, saying, Who is like unto the beast? who is able to make war with him?

(From the NIV Bible)