The Scar is a fathomless rift located in the wastelands of Okanos in the far east of Elyria. The gaping chasm threatens to expand and tear apart the whole world. There is but one thing stopping it. The Thirteen Towers, suspended above The Scar, are connected by 12 chains to the surrounding earth. These Towers interlink and interchain to form one vast fortress which was watched over by the Elyrian army at the Observatory.
When asking Mavda about The Scar, she tells Aeron that it is a deep valley, and no one knows what is at the bottom. She does tell him of some rumours, which state that whatever is down there is connected to the "Other World".
The Scar was created at the same time as The Cataclysm occurred, 50 years ago. It was the Elyrian army's fault, for it happened during the "Final Experiment", or the creation of the Thirteenth Master.