The First Cataclysm shattered Aranna into a thousand ley lines
The First Cataclysm (also known as the Endtime, and to the Elves as Turmanar) was a catastrophic event caused by the meeting of the Sword of Zaramoth and the Shield of Azunai at the end of the First Age.
When these two artifacts clashed during Azunai and Zaramoth's legendary confrontation on the Plain of Tears, a powerful magical backlash was released, tearing the souls from the bodies of all those nearby. These spirits rushed into the River of Souls beneath the land, splintering Aranna into a thousand ley lines. Destruction swept across every corner of the continent as a result, turning much of it into a barren wasteland. The stars shifted in the sky above, and the Second Age began.
The Dryad race was created due to the magics that were released in the wake of the Endtime.
Dungeon Siege II[]
During the events of Dungeon Siege II, Valdis attempted to recreate this phenomena, and eventually succeeded in doing so, bringing about the Second Cataclysm. Only after did he learn that he had been manipulated into doing so by the Overmage of the Cinbri, who wanted to return Aranna's magic to the state it was in before the First Cataclysm.