Rathalos is a recurring type of monster from the Monster Hunter series, and the flagship monster for the original Monster Hunter. It is sometimes known by its epithet "King of the Skies" and belongs to the Flying Wyvern family of monsters. In addition to its female counterpart, Rathian, there are a number of Rathalos subspecies in existence, such as Azure Rathalos. 

Armor, in both Blademaster and Gunner variants, can be created from materials procured from hunting Rathalos.

Super Smash Bros. series

Super Smash Bros. for Nintendo 3DS/Wii U

In Super Smash Bros. for Nintendo 3DS/Wii U, the Rathalos Mail, an armor created with materials obtained on Rathalos in the original series, is featured as a DLC Mii fighter costume exclusive to the Mii Swordfighter.

Super Smash Bros. Ultimate

In Super Smash Bros. Ultimate, Rathalos is featured as both a boss and an Assist Trophy. It can use powerful melee attacks thanks to its claws, breathe fire or use stunning attacks. It is seen flying around the map before its actual fight in World of Light and serves as a boss in the Classic Mode routes of Yoshi, Marth, and Duck Hunt.

Dragalia Lost

During the "Monster Hunter Primal Crisis" event, Rathalos could be acquired as a playable Dragon via the event's item summoning. Its deviant counterpart, the Dreadking Rathalos, can be also be acquired via normal summoning. Both appear as bosses during the event.

Official Description

A massive fire-breathing dragon from another world. Known as the King of the Skies, it makes deft use of its flying ability to rain down death from above. Its fearsome flaming breath has also earned it the moniker of Fire Wyvern.

Official Description (Dreadking Rathalos)

The Dreadking rules the skies, and its massive body, ebon wings, crimson breath, and noble pride serve as proof of its sovereignty. It pays little heed to mere humans, but any fool enough to violate its territory face a terrible judgment.