Mightyena is a quadruped Pokémon that is based on a hyena. Its fur is mostly short and gray, but there is shaggy black fur on its lower legs, tail, and in two thick strips starting behind its eyes and running the length of its body. It has dark, triangular streak patterns below its eyes, which are red with yellow sclerae. Its ears are rhombus-shaped with dark insides, its nose is red, and it has gray paw pads.
Mightyena lives in a pack in the wild. As a member of this pack follows the orders of its leader and chases down prey. It gives obvious signals when it is about to attack, as it starts to growl deeply and flattens its body. Mightyena defeats foes with perfectly coordinated teamwork. If its Trainer is very experienced, it will always obey their orders. As depicted in the anime, Mightyena is prone to licking the faces of the people of which it is fond. This species lives in grassland areas.
Four Mightyena debuted in A Bite to Remember, all under the ownership of Katrina. They were used to help Katrina protect a Pokémon reserve. One of them started out as a Poochyena in the episode, but it evolved after befriending Max.
Ruby's Poochyena, Nana, evolved into Mightyena in Guile from Mawile as the boy met up with Steven. With her increased strength and capacity for better handling advanced techniques such as Hyper Beam, she proved to become a force to be reckoned with, able to defend the boy against his powerful father Norman, and outdo Sapphire's Rono when he was attacked by surprise.
It shares some similarities with both wolves and hyenas. The design may have been influenced by domestic breeds like the German Shepherd Dog, a breed with personalities that are heavily influenced by their owners. German shepherds also commonly come in black and gray colorations. Its appearance may also be based on a brown hyena. Mightyena's shiny appearance as well as the fact that it is a pack animal is reminiscent of a spotted hyena.
Mightyena may be a combination of mighty and hyena.