- Order: Saurischia
- Suborder: Wyvern Feet
- Infraorder: Armor Shell Wyvern
- Superfamily: Flying Wyvern
- Family: Rath
One of the most recognized monsters, Rathalos are a part of the Flying Wyvern classification along with their female counterparts, the Rathian. There are three known species of Rathalos: The Old World Species, New World Species, and Val Harbar Species. There is also two genetic mutations of the Rathalos, the Azure Rathalos and the Silver Rathalos.
Rathalos of the Old World inhabit areas such as the Forest and Hills, Tower, Gorge, Old Swamp, both Volcanoes, Highland, Ancestral Steppe, Heaven's Mount, Volcanic Hollow, Tower, Ruined Ridge and Misty Peaks. Rathalos of the New World inhabit the Ancient Forest.
Rathalos fear almost nothing else found in their habitat range, except other large predators and Elder Dragons. Rathalos may prey on lesser wyverns, particularly bird wyverns such as Jaggi, Velociprey and their alpha forms or pelagus such as Bullfango. Only certain predators in a Rathalos' territory are strong enough to fight back if a Rathalos is attacking. Foremost among them are other wyverns and large monsters that live in the same habitat. Such predators include Lagiacrus, Seregios, Tigrex, Gore Magala, Brachydios, Deviljho, Stygian Zinogre, Agnaktor, Lavasioth and the rare Rajang as they are large and powerful enough to threaten and possibly kill an adult Rathalos, but it wont go down without putting up a fight!
Rathalos is one of the few monsters who sits at the top of New World habitat's food chain, namely in the Ancient Forest region where other monsters such as Great Jagras, Tobi-Kadachi and even Anjanath would try their best not to cross the line set by the male Fire Wyvern. However, Elder Dragons and powerful invaders like Deviljho and Bazelgeuse would take more than Rathalos' established dominance to be fend off, at times Rathalos would actually avoid confrontation with said monsters altogether for survival's sake and wait for them to move on or being dealt with by Hunters. Rathalos presumably gain sustenance in the New World by preying on Aptonoth like it does in the Old World.
An adept flyer, Rathalos often use fire-balls to attack foes from both land and air. Rathalos are able produce these fireballs due to it having multiple flame sacs. Rathalos have powerful hind legs, making them fast on the ground, as well as giving them the capability to launch devastating claw attacks from the air, often severely injuring its target. While in the air, they are also capable of diving to claw foes on the ground. A Rathalos' claws contain a potent toxin used to injure and sap the preys strength. Rathalos, like many others of its kind, have a powerful roar that they use to intimidate rivals and stun prey. Its bright red scales serve as camouflage in volcanic areas.
The Rathalos' body build, along with the Rathian's, differs between the Old World and New World. In the New World, Rathalos have a wider wingspan, while in the Old World, their wingspan is less. Their elemental weaknesses have also changed. This is due to them being Subspecies of each other.
Some rare individuals in the Old World appear to be older, with a darker red tint, more developed and longer spikes on their back and tail, larger leg muscles and increased flying abilities. It is unknown if this is caused by aging or a mutation.
Like most true flying wyverns, Rathalos possesses the cunning, speed, and strength to fell almost any threat or prey they come across in the wild though they will rarely challenge anything larger than themselves outside of their territory. Rathalos are especially aggressive during mating season. After mating with a Rathian, Rathalos will patrol his territory from the skies, looking for any threats to attack and eliminate from the his territory.