Terrible wyverns called the 'Kings of the Skies'. Together with Rathian, they stake wide territories centered around their nests. Rathalos descend on invaders from the sky, attacking with poison claws and breath of fire.
- 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, Astalos, and the rare Rajang as they are large and powerful enough to threaten and possibly kill an adult Rathalos, but it won't 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, the king of the skies isn't the only top predator here as the likes of Tigrex, Glavenus and especially, Nargacuga, have arrived in the New World and are ready to challenge the Rathalos. Elder Dragons and powerful invaders like Deviljho and Bazelgeuse would also take more than Rathalos' established dominance to 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. Despite these threats, the Fire Wyvern still has a few tricks up its sleeves to fend off would-be attackers. Most notably, its ability of flight immediately puts it at an advantage against its land-dwelling rivals. Rathalos presumably gains sustenance in the New World by preying on Aptonoth, as it does in the Old World.
Oltura is a natural predator of the Rathalos as it feeds exclusively on the whole species in order to grow and molt to adulthood. The Rathlos fears it immensely and will flee as quickly as they can in order to avoid the rage-rays hole Olutra resides in. The reason is due to the rage-rays having an hypnotic effect which can lure the Rathalos in to their deaths.
An adept flyer, Rathalos often use fire-balls to attack foes from both land and air. Rathalos are able to 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, has a powerful roar that they use to intimidate rivals and stun prey. Its bright red scales serve as camouflage in volcanic areas. The Wyvern is also noted for its considerable strength. As shown in World, the Rathalos is a capable fighter with enough strength to lift up some opponents and slam them onto the ground as if they were mere ragdolls.
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 his territory.