Description taken from Arcade version of this game

Ghosts 'n Goblins puts you in the role of a good and honorable knight who must rescue a beautiful princess. You run and jump through six horizontal- or vertical-scrolling levels while battling zombies, ravens, flying knights, ghosts, bats, demons, skeletons and other horrific nasties. Depending on which weapon you have most recently picked up, you brandish an axe, a lance, a cross, a dagger or a firebrand. You can only tote one weapon at a time, however.

Two hits from an enemy attack will kill you. The first hit destroys your armor and leaves you wearing nothing but underwear. You can retrieve your armor by jumping up at certain hidden areas throughout the game. When you hit the right spot, a pot falls from the top of the screen. Grab this pot while you are in your skivvies and you are once again a knight in shining armor.

A map shows you the various levels you must brave: graveyard and forest, town, caves, bridge, lower level castle and upper level castle. At the end of each stage, you must destroy a giant boss, such as a dragon or a demon. ~ Brett Alan Weiss, All Game Guide