Dragons (ドラゴン, Doragon) are the strongest living creatures on the planet. Their scales are very hard and they can blow out red hot flames from their mouth. They can cut down rocky mountains with their tails and can send large trees flying with a beat of their gigantic wings. The corpses of Dragons are extremely valuable, with every single part of them able to be sold. The money exchanged for the remains of a 25m Dragon can allow a small village to live in comfort for a whole year.
Dragons are resistant to all natural powers like fire, water, earth and wind, and this includes the light energy of a Photon Carrier. The only thing that is effective against dragons is fighting energy used by the Rato Tribe, Koki. Dragons are hunted by groups of the Rato Tribe in what they call Dragonbanes (竜退治 (ドラゴンベイン), Ryū Taiji (Doragonbein)). The Rato conducts Dragonbanes to keep all of the Dragons in one spot, known as the Sacrificial Fort (贄の砦, Nie no Toride), as their enormous power would be harmful to the world. As such, no Dragons exist outside the Fort. Koki is actually the will and resolve of hitting the Dragon or Tsuta with all of one's emotions and being, and accepting all of the Dragon or Tsuta. After learning of the origin of Dragons, Lacile and Noish were able to hurt them. Lululola and Popol were also able to defeat Dragon Knights.
The Tsuta Tribe are said to be followers of Dragons. In actuality, Dragons are the form taken by Tsutas who are near death and have lost their sense of self. This is perhaps a result of the Tsuta Tribe's self-suppression. Dragonification (竜化) can be delayed if the Tsuta had strong willpower, like Illuyankas' father, the 50m dragon and presumably the former Tsuta King, but it can't be stopped.
An average dragon is 25m long. A couple years ago 25m would be classified as a large dragon, but they have been growing larger.
A 50m Dragon, the largest ever recorded, appeared near the front lines of the Rato Tribe's town.