The game takes place in the country of Mythgard, where the protagonist, The Jewel Master must traverse the harsh lands ranging from scorching deserts to rugged mountains and through long forgotten ruins to collect the 12 elemental rings and save Mythgard from the clutches of the Demon King, Jardine the Mad.
The game is a side-scrolling action-adventure. It introduces the ability to constantly customize your attacks and movement styles through various equippable rings. Using the "A" and "B" buttons as his left and right hands, you can then equip two rings to the corresponding hand. The "C" button is used for jumping.
Source: Wikipedia, "Jewel Master", available under the CC-BY-SA License.