Entei is a massive brown lion-like creature 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.
It has the Pressure ability 100% of the time. Like Raikou, it likes to course headlong across the land in a display of its raw power; but instead of dishing out lightnings, it spouts flames that are hotter than magma. It also sends up massive bursts of fire that utterly consume all that they touch. It is also said that every time it roars a volcano erupts.
The term "Legendary beasts" is the only technically correct term to refer to Entei and its companion legendaries, due to the fact that rather than having specifically canine or feline traits, all three of the trio share both.
Entei bears a strong resemblance to the Chinese Guardian Lions of Chinese lore and the Shisa of Okinawa legend; both of which are lion-based creatures of Asian folklore. Entei also exhibits lion like behavior and has been known to roar as such.
In Japanese, the name Entei literally means "Flame Emperor".
Entei is the only legendary beast not to have a patterns on its body. Raikou has lightning-like patterns and Suicune has diamonds on it.
According to research, when Entei roars, a volcano will erupt on the other side of the world.
Entei doesn't have a tail unlike Raikou and Suicune. However, the ash/smoke-like flowing mane on its back slightly resembles a tail.