5000 years ago, the war between Good And Evil and the Old Ones was coming to an end. It was at this point that one of the Old Ones, called Hastur, was sent to Earth to develop weapons to defeat the forces of Good And Evil.
Setting up his base on a remote island, Hastur began to develop the aforementioned weapons. Among the weapons that Hastur developed were the forces that would later became known as the Hollow and the Nothing.
However, it was still too late to turn the tide of the war. The Old Ones were sealed up in their empty dimension, and the Hollow and Nothing were take by the forces of Good And Evil as spoils of war. The Charmed Ones would have encounters with both these forces, while never knowing of their true origins.
The forces of Good And Evil then sank the island, so no one could find it. However, before they could do that, Hastur had placed himself in a state of suspended animation, in a sarcophagus, located inside a huge temple.
Over the subsequent centuries, the island would rise and sink, due to underwater volcanic activity.
On one occasion, in 1916, during one of the times that the island was on the surface, a merchant marine named George Morris, after escaping a German sea raider, stumbled upon the island. He later claimed to have seen "terrible things" on the island. However, when he returned to civilization, no one took him seriously, except the Inner Circle, who believed him. Yet when they tried to relocate the island, they were unsuccessful, the island had sunk once again.
Rex and Hannah on the island
Upon arrival at the island, they soon discovered the truth about the island and the connection to Hastur.
The group soon discovered Hastur himself , in suspended animation. It was at that point that the group was captured by Herbert West and Johanna Martense, who had come to the island to free Hastur. Johanna had used her magic to raise the island to accomplish this.
When Rex refused to help Johanna and West, Johanna had West lock Rex, Hannah, and Randolph up. However, the group managed to escape the island, before it once again sank beneath the sea.
What the two former Warlocks didn't know, however, was that Johanna and West had managed to transport themselves, and Hastur, off the island before it sank. Soon after, Johanna awakened Hastur and she and West vowed to do his bidding.
Rex and Hannah Chronicles Story No. 46: The Island