Scourging the Throwing Stones
In an event known as the Scourging of the Throwing Stones a numberless horde of feral orcs managed to pass through the Underdark and enter the vast cave complex which sits below the archipelago of the Throwing Stones. The islands were well defended by the Sylvan warships but the islands themselves were largely undefended and quickly fell victim to the orc horde. The orcs destroyed everything that they could find and killed all the denizens of the island.
Following the massacre, the elves retaliated with an overwhelming force which killed all orcs on the surfaces of the islands. With nothing less on the island it was deemed too costly to attempt to kill the orcs in the caves below and thus the islands were abandoned to the orcs.