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Sega established itself as one of the biggest names in the arcade business in the late 1980s, thanks to the success of titles such as Golden Axe, Space Harrier, and one of our old favourites, Altered Beast.
Debuting on coin-op hardware in 1988, Altered Beast was a side-scrolling beat 'em up set in Ancient Greece that cast players as a resurrected Roman centurion with shape-shifting abilities.
The game begins as the warrior protagonist's eternal rest is brought to an abrupt end by Zeus, who tasked him with rescuing his daughter Athena from the clutches of underworld demon Neff.
Players battled their way through five stages, slaying a menagerie of creatures from the annals of mythology along the way. It would have been another bog standard addition to the action genre was it not for the memorable transformation system.
The centurion gathered spirit balls on each level. Collecting a single orb beefed him up into a muscular powerhouse, while snagging a second turned him into a man-beast hybrid with devastating special abilities.
There was a different creature to control on each stage - from the graveyard level's Werewolf to the Weredragon of the underworld - and watching foes fall like dominoes under their savage force was among the highlights of the experience.
Each level ended with a showdown against Neff, with the player in beast form and the demon taking on the shape of a different screen-filling horror each time.
The boss battles also stick in our mind. Who could forget squaring off against Neff in the guise of an ogre-like monstrosity with endless heads, or being charged at by an armoured rhinoceros-esque creature during the final confrontation?
We'll always remember Altered Beast for its sound effects, too, with the game making effective use of digitised speech and even borrowing a howling effect from the 1981 movie An American Werewolf in London to add style to its transformation sequences.
Altered Beast was well received in the arcades and a successful release on home formats followed. The Sega Mega Drive version is by far the most memorable, preceding Sonic the Hedgehog as the console's pack-in game in the UK and North America.
Although the game was a smash hit for Sega, it never grew into a strong franchise, which is a shame considering how much mileage the concept had.
Sequels could have introduced additional beasts to transform into, new foes from Greek scripture and new deities to embark on missions for, or even wage battles a la God of War's Kratos.
A follow-up of sorts was released for Game Boy Advance in 2002 in the form of Altered Beast: Guardian of the Realms, which revisited the side-scrolling gameplay and introduced new beast forms, additional power-ups and destructible environments.
Sega attempted an Altered Beast revival in 2005, reimagining the concept for PlayStation 2 as a modern day science-fiction tale. Players took control of a "Genome-Cyborg" who was capable of altering his DNA to take on the shape of various beasts.
The game had little in common with the classic that stole our hearts in the 1980s and was critically panned.
We would like to have seen Sega take the concept in an entirely different direction, retaining the setting of Ancient Greece and reviving Altered Beast as a 3D hack n' slash offering in the vein of God of War, but that particular ship has surely sailed.
Do you have any fond memories of Altered Beast? Post a comment below!