From the back of the box:

After centuries in captivity, King Barius, Lord of the Demons, has escaped. In his fury he has cursed the peaceful land of Rolan. Hordes of dark creatures roam free in the countryside. A desperate cry goes out...are there any warriors brave enough to free the people from the curse?

From Wikipedia:
"Like Nintendo's Zelda adventure series, the player goes from screen to screen and defeats enemies with a sword while finding items from monsters and treasure chests. The player is allowed two items at a time: one weapon and one sub-item; picking up a different weapon or sub will switch out the current one. The character starts with a sword but can find a fire wand that deals ranged attacks at the sacrifice of attack power. Other items include a hammer for breaking down barriers and a potion for restoring all health. The player can also pick up another of the currently equipped weapon to gain a temporary boost to attack power, or an armor jacket to raise defense temporarily. These temporary boosts return to normal after a level is beaten. More permanent power-ups come in the form of strength gloves and heart containers, which upgrade attack and defense respectively.

The game can also be played with another player if the two individuals link their Game Boys together while the game is inserted."

Source: Wikipedia, "Rolan's_Curse," available under the CC-BY-SA License.