In Altered Beast, Zeus resurrects a warrior and gives him the task of rescuing his daughter from the evil Neff. Not sure why Zeus couldn't do it himself, but this warrior seems special because he can turn into a beast.
You start each level in human form. Some enemies will drop and orb, collect 3 and transform into a beast. Each level has a different beast: werewolf, dragon, bear, tiger and a golden wolf. The beasts have different attacks, even though the attacks aren't really associated with that particular beast e.g. a bear has a spin jump attack, wolf has a fireball.
You move from left to right, mainly punching and kicking enemies as you make your way to the end of the level where you will fight a boss.
The graphics are okay, the sprites seemed a overly large meaning the screen was a bit cluttered.
The gameplay is quite clunky, sometimes the hit detection seemed a bit off, or the amount of space you have to dodge is insanely minimal. I had a hard time understanding how to attack the bosses without taking damage myself. Sometimes this was a problem with normal enemies too.
I played this in the Sega Genesis Collection on Steam which runs inside an emulator. You could rewind as much as you like and I was rewinding constantly. It seemed extremely difficult to avoid enemy attacks, and some I was convinced were actually impossible to dodge.
There's only 5 levels, and by using the Rewinds and Save states in an emulator, you can easily be done within 20 minutes.
It's clunky, it's unfair, it's short. It's just not very good.