Völgarr the Viking Gauntlet

From the introduction: Rise Warrior! You are on a mission from Odin to slay the greedy dragon Fáfnir, who has locked himself away in a tower sealed with ancient magic that even the gods cannot penetrate. To reach the tower you will have to traverse six worlds, each containing their own monsters and natural dangers. Each world will also be inhabited by a guardian, a beast possessing unparalleled power and dominion over their region in exchange for their servitude to the dragon, that you will need to defeat before you can proceed, their lifeforce being tied to the protections on the tower. Facing a hopeless task… Will you heed Odin’s call? And become a viking legend?