|Alias(es)||The Heart of the Island|
|Episode(s)||Across the Sea|
|Found By||Unknown, perhaps Jacob's Mother|
The Source, or the "heart of the Island", is a cave on the Island with a glowing interior filled with warm gold light. It contains high levels of electromagnetism and is constantly fed by a natural stream of water.
It is believed to be responsible for most paranormal phenomena experienced on the island, and is the source of several other energy pockets around The Island. According to Eloise Hawking, the energy pockets connect to similar pockets around the world, while Mother stated it is the source of life, death, and rebirth, and that anyone who enters would suffer a fate "worse than death". According to her, people who sought it could put it out, hence the need for it to be protected. Both Jacob and Mother believed that putting out the Light could have a negative impact on the world. The light inside the cave seems to appear brighter in Across the Sea.
Only the protector can find the cave and lead people to it. The only people depicted in the series entering the cave were Jacob's Brother, Desmond Hume, and Jack Shephard. In anger over their mother's death at his brother's hands, Jacob beat his brother and then sent him floating unconscious down the stream and into the cavern where the Light originated. Moments later, the Black Smoke burst from the cave and flew into the jungle. Jacob later found his brother's corpse, laying lifeless on a rock. Centuries later, Jack, Desmond and The Man in Black ventured to the cavern, after Jack had assumed Jacob's role as the protector of the island.
The cave contains a man made pool of water with a stone cork at the center of it, which plugs a gaping hole. Two water ducts supply water to the pool, and four water ducts carry water out, which probably carries unique properties of The Source throughout the Island.
The stone cork seals the hole of The Source, and has four lines of inscriptions on it. The first two lines appear to be written in Egyptian hieroglyphics while the final two are written in cuneiform.
Line 1: "Embrace that which the Balance hath weighed, let a path be made for the Osiris in the Great Valley, and let the Osiris have light to guide him on his way."
Line 2: "He hath reconciled the Two Fighters (Horus and Set), the guardians of life."
Line 3: "Break the immovable yoke that we may sleep."
Line 4: "That silence may reign and we may sleep."
After being sent into the cave, Desmond Hume walked into the pool. With his immunity to electromagnetism, he successfully removed the cork, which stopped the stream that was flowing into the cave. The remaining water disappeared into the hole in the ground with a rotating sound, which extinguished the Light. This seems to indicate that the absence of water causes The Apparatus to malfunction. A dark orange light began to appear and steam began to emit from the hole. Water stopped running into the cave, indicating that the heart of the Island worked as a circulatory system to The Island, which was implied in the commentary of the episode "Across The Sea".
Mother was the first known Protector of the heart of the Island. Once she realized that it was time for her to find a replacement, she passed on her responsibility to Jacob and manipulated The Man in Black into killing her, freeing herself from said responsibility.
Jacob spent thousands of years protecting the heart while simultaneously looking for a way to kill The Man in Black, whom Jacob considered to be evil. Conversely, the Man in Black also plotted to kill Jacob, so he could leave the Island.
Prior to the construction of the apparatus, the Light was being produced by a natural process. After Desmond entered the cave, he found three skeletons on the ground, indicating that people had entered The Source before. Once The Man in Black learned of Desmond's immunity to electromagnetism, he decided to use Desmond to extinguish the Light and destroy The Island.
Consequences of extinguishing the LightEdit
When the Light was temporarily extinguished, the Island began to sink into the ocean, and it was revealed that the Man in Black was now mortal. Jack and the Man in Black engaged in a fight, resulting in the Man in Black stabbing Jack in the side. However, before he could kill Jack, Kate emerged and shot him in the back, which gave Jack the opening to deliver the killing blow, kicking him over the edge of the cliff and finally destroying the Man In Black.
Restoring the LightEdit
Jack, Hurley, and Ben returned to the cavern, where Jack passed the responsibility of being the protector of the Island to Hurley, Hurley and Ben then lowered Jack down into the cavern via rope, in an attempt to reverse the extinguishing of The Source.
Once inside the cavern, Jack found Desmond lying on the ground in a weakened state after having previously removed the cork from The Apparatus. Jack then secured Desmond to the rope he was lowered into the cavern with, allowing Desmond to escape while Jack put the cork back into place, knowing that doing so would most likely lead to his death. Moments later, the water started running again, and as soon as the water reached the hole, the light returned. After returning the cork to the hole, Jack was transported from the cavern, ending up on the same rock the Man In Black's corpse had been seen on after Jacob had sent him into the cavern a millennia before.
- It was implied in the commentary of the episode Across the Sea that the apparatus inside the cave was built years after The Man in Black was transformed into the monster; this was later confirmed by the Lost Encyclopedia, which states that Jacob instructed early inhabitants of the island to build the apparatus, damming the flow of the light.