A sign near the Lake of Ill Omen warns passerby not to throw anything into the nearby circle of stones. Being the daring soul that he is, Link should throw something into the circle. A strange fish will try to bribe Link into leaving him alone by giving him the Quake Medallion. Using it causes the earth to shake violently. Link can gain entrance to Turtle Rock by using Quake."
"A shy water resident will give up the Quake Medallion."
"Crunch! Link thrusts his sword deep into the Hylian crust to activate the Quake Spell. The ground will shake with tremendous force."
The Quake Medallion is an item featured in A Link to the Past. It is one of three Medallions that can be found in the game, and is one of two Medallions required to complete the game. The Medallion allows Link to do a jump strike in the ground, rumbling the entire screen. The Medallion is required to enter Turtle Rock.
To obtain the Quake Medallion, Link must first obtain the Book of Mudora. Next, he must venture to the Lake of Ill Omen. If Link throws something in the ring of rocks there, a Catfish living there will give Link the Quake Medallion to make Link go away.