Altered Beast is a side scrolling, platform, beat 'em up game. The player controls the centurion, fighting undead creatures and monsters in a setting resembling Ancient Greece, with originally five levels, in a graveyard, the Underworld, a cavern, Neff's palace and base at the city of Dis. One of the enemies, a white two-headed wolf (blue in the Mega Drive version, and a blue ox in the DOS version) upon defeat releases a Spirit Ball, a power-up orb which increase the strength and size of the player character.

Altered Beast is a side scrolling, platform, beat 'em up game. The player controls the centurion, fighting undead creatures and monsters in a setting resembling Ancient Greece, with originally five levels, in a graveyard, the Underworld, a cavern, Neff's palace and base at the city of Dis. One of the enemies, a white two-headed wolf (blue in the Mega Drive version, and a blue ox in the DOS version) upon defeat releases a Spirit Ball, a power-up orb which increase the strength and size of the player character. Three orbs turn the centurion into a beast, which in the original version were a werewolf, a thunder weredragon, a werebear, a weretiger, and the more powerful golden werewolf. Each beast has its own abilities, such as the dragon's flight and lightning, and the bear's petrification. After becoming the beast, the character can face the end-level boss, which upon defeat causes Neff to appear and remove the transformation orbs.

The goddess Athena has been abducted by the Lord of the Underworld. Her father, the great god Zeus, searched for a brave warrior strong enough to save her. He chose a brave warrior who died with honor & courage on the battlefield. Zeus raised the warrior from the grave and granted him the power to morph into a powerful, holy beast in order to do battle against the unspeakable horrors of the Underworld.

Altered Beast is a 1-player sideways scrolling beat-em-up. The game begins with the player controlling the human form of the resurrected warrior. During the levels the warrior will be attacked by a number of flashing animals. Destroying these creatures will result in an orb being dropped. If the player picks up an orb, he will begin his transformation from human into 'Beast'. Once 3 orbs have been collected, the transformation is complete. In beast form the player's character is much faster and stronger than in the human form, and also has the ability to throw fireballs at the enemy. At the end of each stage, after the boss fight, the player's special powers are taken from him and he once again reverts to human form.

The action in Altered Beast is untypically slow-paced and sedate for a game of this nature, but the game's premise and graphical flair helped to separate it from other rivals of the genre.

Alex and Stella from "Alex Kidd" are declared dead in the first stage of this game (Alex and Stella stones).

The small tail swinging gryphon that appears often in this game makes a comeback in "Golden Axe".

You were once a Roman Centurion. You died bravely in a battle. Now, a hundred years later, you have been called back from the grave by Zeus, God of Thunder. Even as he grants you new life he gives you a mission. You must rescue his daughter Athena from the eveil clutches of Neff; Lord of the Underworld.

From the surface to the very heart of the Underworld you must journey, fighting Neff's undead army every step of the way! Zombies, demons, gargoyles, three-headed Wolves.

But in this life you have been given an edge... the power to transform into magical beasts of awesome power! From a man to a superman... to a werewolf, were-drageon, were-tiger and the ultimate... a Golden Wolf! Each form has supernatural abilities. You'll need them all... for Neff is a fearsome enemy.

Fail, and Athena's fate will be unspeakable. Win... and you may take a place in the Pantheon of Immortality! Remember... Never say die!

Converted from the popular Sega arcade game.

Destroy all enemies to rescue the fair maiden. Your powers increase when you destroy certain enemies and take their energy; once you achieve a certain energy level, you can alter your shape into that of a beast, with additional abilities. At the end of each level is a "boss" monster that you must defeat to travel to the next area.