Great Cataclysm

Legend of the Great Cataclsym
"The Hero's triumph on Cataclysm's Eve, Wins Three Symbols of Virtue, The Master Sword He will then retrieve, Keeping the Knights' line true." - Pedastal of Time, The Legend of Zelda: A Link to the Past

Theories Surrounding the Great Cataclsym

 * According to ALttP, the Great Cataclysm occurred when the Gerudo King of Thieves, Ganondorf, entered the Sacred Realm (or Golden Land) and seized the sacred Triforce for himself. The Great Cataclysm then led to a prolonged and bloody conflict known as the Imprisoning War that resulted in Ganon's (as Ganondorf came to be called) "imprisonment" inside the Sacred Realm, which became the Dark World due to his vile influence.  These events were chronicled in The Legend of Zelda: Ocarina of Time, when the Hero of Time pulled the Master Sword from the Pedastal of Time and opened the gateway to the Sacred Realm.  In doing so, he was sealed in the Sacred Realm for seven years, and Ganondorf used the gateway he opened to enter the Sacred Realm, claiming the Triforce with blood-stained hands.  The "three symbols of virtue" the Hero supposedly won were the three Spiritual Stones (which possibly became the Pendants of Virtue centuries later).  The Hero's heritage "keeping the Knights' line true" seems to indicate that the Hero of Time, the Hero at the time of the Great Cataclysm, was a descendant of the Knights of Hyrule.  If this is so, it would lend credence to the possibility that the Link from ALttP is a descendant of the Link from OoT since the one from ALttP was noted as being the last of the bloodline of the Knights of Hyrule.