Phelios is a vertical scrolling shoot 'em up that has the God Apollo flying on the back of a Pegasus. The game borrows themes from Greek mythology. Players control Apollo on a quest to save the goddess Artemis, who has been imprisoned by the mythological beast Typhon.
Gameplay wise, it is very similar to other shoot 'em ups of the time. There are different power ups to collect which make the main weapon more powerful or more useful (horizontal shot). There are also power-ups to increase speed, which become essential for dodging later in the game.