Entei is one of the three "Legendary Beasts" that are featured in Pokémon Gold, Silver, and Crystal. According to legend, the Legendary Beasts were reincarnated by Ho-Oh from the spirits of three Pokémon which died in the fire that gave Burnt Tower its name. They are awakened in this tower in their first video game appearance. Entei is a lion-like creature covered in brown fur with a long, thick mane covering its neck. It has gray plates surrounding the cape that makes it look as if smoke is coming out of a crater on its back. Entei has white paws and black cuff-like bands on its legs, It has a red face with a white plate that resembles a handlebar mustache on its face, and a three-pointed yellow crest on its forehead. Entei's head appears to resemble a kabuto, a samurai helmet. Myths say that it is born during the eruption of a volcano, and that a new one is born along with each volcano. Entei is an embodiment of magma, being able to launch powerfully searing, fire that is hotter than magma from its mouth. When it roars, it can make a volcano erupt on another part of the globe. As a member of the legendary beast trio, Entei is constantly on the move with no set place to hang around in.
Entei was a main character in Pokémon 3: The Movie. He is an illusionary Entei that appeared to Molly Hale after she made a wish to the Unown, serving as a replacement father for her while her real father was trapped in the Unown dimension. He did everything Molly asked for, even kidnapping Delia Ketchum so she can be Molly's mother and providing her with Crystal Pokémon for her to battle Brock and Misty with when they entered the tower that Entei had created to rescue Delia. When Ash attempted to confront Entei to get his mother back, his Totodile and Cyndaquil were rapidly defeated, with Pikachu only lasting longer without fairing any better, and even Charizard was only able to hold Entei off without actually defeating it. However, when Entei was about to kill Charizard, Molly finally decided that she wanted things to be real again. Accepting Molly's decision, Entei helped Pikachu and Charizard defeat the now out-of-control Unown, subsequently bidding Molly farewell and assuring her that he would always be in her dreams.