The Isle of the Four Sisters was an island that existed in the Silver Sea. Four sisters lived there and kept asleep a huge monster that lived beneath the island with a song. When the sisters were killed by the Shadow Lord, the giant beast woke and smashed the island, causing it to sink beneath the sea.
Four Sisters lived on an isle in the Silver Sea a long time ago. They sang to each other and their voices soothed the island. Some sailors who passed by the isle, claimed to have heard to singing although to most it sounded like rustling leaves, lapping water, small animals and such.
The Shadow Lord arrived at the Isle and immediately imprisoned the Four Sisters on a corner of the isle because he hated the singing. When they would not stop singing, he killed them all. As the singing stopped, a giant beast awoke and began tearing the isle apart. Soon the isle and the Beast sank inside the sea and were never seen again.
Josef wrote down the Tale of the Four Sisters for Lief and realised the truth about the Four Sisters in Deltora. He wanted to tell Lief what he knew but died before he could. Eventually, Lief figured the meaning about by himself.