Interdimensional beings influenced the beginnings of various human civilizations. They were humanoids but stood at an average height of nine feet, and their heads were elongated. Instead of bone, their skeletons were made of a crystalline property which held magnetic qualities.
"Collectors. They were archaeologists."―Indiana Jones[src]
According to Harold Oxley, they were not from space, but from the "space between spaces", and they traveled with flying saucers. Thirteen beings arrived on Earth about 7,000 years before the mid-20th century. According to the murals found in the entrance of Akator, they taught the Ugha agriculture, irrigation and technology. The Ugha worshiped them as gods and carved out the vast Nazca Lines in the deserts of Peru as a tribute. Indiana Jones noticed that the Ugha had the custom to wrap their children's heads to cause an elongated shape, in order to "honor the gods". Jones also discovered that the beings' other major activity was, much like human archaeologists, the collecting of artifacts from many ancient cultures all over the world.
Those thirteen beings were situated in the Temple of Akator, perhaps as a kind of ruling council. According to Irina Spalko they thought and acted as a hive mind and a single being. For some reason they were left there as crystal skeletons. Centuries later, Francisco de Orellana found the temple during his search for the legendary town of El Dorado. Among other treasures, he took the crystal skull of one such skeleton. During his trip back, the mental power of the skull forced him to return it to Akator, but he was killed before he could do so and buried together with the skull. The legend about the robbery spread and said that he who would return the skull would receive great power.
More beings visited Earth to search for the missing thirteen. Two of their vehicles crashed in what became USSR territory, including an event in Siberia in 1908 near the Tunguska River. A third crashed in Roswell in 1947. Jones was part of the team ordered to examine the remains of a "mutilated" body from the site in absolute secrecy. The body was kept in Hangar 51 in Nevada until it was stolen by Irina Spalko's team ten years later.
When Jones had recovered the missing skull and reached the Temple of Akator with his companions, followed by Spalko and her soldiers, they found the thirteen crystal skeletons, one of them headless. Spalko joined the skull to the skeleton, which, through Oxley, started to speak in the Mayan language, saying it would give them a great gift. Spalko demanded to know everything, and the thirteen started firing knowledge out of their skulls into her eyes. The Temple started to collapse, opening a portal to another dimension. Indy's band managed to escape from the temple.
Meanwhile, the thirteen skeletons joined together to form a single being right before Spalko. The knowledge from the beings began to overwhelm her and she begged it to stop. But the being continued the transfer and Spalko's eyes ignited and her body disintegrated. Her remains were sucked into the portal and the other Soviets in the room were pulled in as well by their weapons and ammo belts.
Jones, Marion Ravenwood, Mutt Williams and Oxley found their way out above the valley of Akator, and observed the temple's collapse, revealing a huge flying saucer which vanished soon after. Indy asked Oxley if the ship went into space. "Not into space," he replied, "but into the space between spaces."
- Indiana Jones and the Kingdom of the Crystal Skull
- Indiana Jones and the Kingdom of the Crystal Skull novel
- LEGO Indiana Jones 2: The Adventure Continues (Non-canonical appearance)