The game is set in Ancient Greece and follows a player character chosen by Zeus to rescue his daughter Athena from the demonic ruler of the underworld, Neff.

Altered Beast was the pack-in game when the Genesis launched in North America and the Mega Drive in Europe.

Combat takes place across five levels set in Ancient Greece and populated by aggressive undead creatures and monsters resembling those from Greek mythology.

The game's player character is the resurrected Roman Centurion, given extra power by Zeus so they can battle Neff and his supernatural minions.

Collecting three Spirit Balls allows the player character to transform into a powerful beast form, increasing their combat abilities before having to face Neff at the end of the level.

The dragon can unleash lightning bolts and an electric barrier, the bear has a petrifying breath that turns enemies into stone, the tiger can throw fireballs in a zig-zag pattern, the wolf can throw direct, but weak fireballs and has a powerful thrust attack, while the golden werewolf has the same abilities as the wolf form.

He took inspiration for the game from The Howling and the music video for the Michael Jackson song "Thriller",[7] as well as movies by Ray Harryhausen, and chose the Greek setting for the powerful characters he had in mind.

[10] Uchida admitted that he struggled during production because it was his first game he developed, and so he leaned on his lead programmer to help create balance in the gameplay.

[7] Uchida was not impressed by the initial concept art, so he worked with an artist to sketch out his specific ideas on character design.

Discussions took place but a deal could not be reached with the owner of the patent of the pressure-sensitive device over the small number to be ordered.

As a result of its popularity, it was selected to be ported and made the pack-in game for the Sega Genesis and Mega Drive in North America and Europe.

By the time he went to the US three years later, all of the available consoles instead included Sonic the Hedgehog,[7] which replaced Altered Beast in part over concerns the latter's themes of zombies and magic were not popular in the Bible Belt.

Others provided additional beasts to mutate into, such as a humanoid lion, shark, and phoenix forms seen in the Famicom version, ported by Asmik.

The Games Machine gave the Mega Drive version a positive review on the faithful arcade conversion.

[27] Contrary to their praise for the Mega Drive port, The Games Machine called the Master System version "a middling conversion of a nice coin-op".

"[37] S: The Sega Magazine stated that there are better arcade conversions on the Master System and that Altered Beast, while having a passable soundtrack, suffers from poor animation and control issues.

[43] Its re-release for the Wii's Virtual Console was given a lukewarm reception by GameSpot and IGN, describing the game as merely decent with some nostalgic value.

Sweet told Spin magazine that the title meant "whatever is inside you that someday might explode, and maybe you don't know it's there", which he found similar to the game, where "you have to find these little power-up things, and when you eat them you become the Altered Beast, this other creature that's really powerful and violent".

[51] The character Neff, in his Rhino form as the boss of the game's final level, appeared in the 2012 Disney film Wreck-It Ralph, along with Sonic the Hedgehog villain Doctor Eggman.

Apostle Studios achieved the world record of highest score with 6,621,500 on the Sega Genesis, while Samuel Clemens of California placed second with 1,008,300 points on July 19, 2022, on the PlayStation 4.