Interdimensional beings

Extra-dimensional beings have influenced the beginnings of various human civilizations.

Akator
Thirteen beings arrived on Earth about 5,000 years ago. They were humanoid but their heads were elongated. Instead of bones, their skeletons were made of pure crystal which had magnetic qualities. According to Harold Oxley, they were multidimensional beings not from space, but from the 'space between spaces', and they traveled with flying saucers.

According to the murals found in the entrance of Akator, the aliens taught the Mayans agriculture, irrigation and technology. The Mayans worshiped them as gods and carved out the vast Nazca-lines in the deserts of Peru, in order to honor their gods. Indy noticed that the Mayans had the custom to wrap their children's heads to cause an elongated shape, in order to 'honor the gods'.

Thirteen of those aliens 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, presumably dead, as skeletons. Centuries later, the skull of one such skeleton was removed and the legend said that he who would return it would receive great power. Francisco de Orellana tried to find the temple and return the skull; however, he died before he could ever find the temple.

More aliens kept coming back to Earth to search for the missing thirteen. One of their vehicles crashed in Roswell in 1947. Indiana Jones was part of the team ordered to recover the remains of a 'mutilated' body in absolute secrecy. The body was kept in Hangar 51 until it was stolen by Irina Spalko's team ten years later.

When Jones, Spalko, and their bands reached the Temple of Akator, they found thirteen crystal alien skeletons, one of them being headless; Spalko joined the skull to the alien's skeleton, which, through Oxley, started to speak in the Mayan language, saying it would give them them a great gift. Spalko demanded to know everything, and the the thirteen alien skeletons 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 while the thirteen skeletons joined together to form a single being right before Spalko. The knowledge from the aliens overwhelmed her and she disintegrated; her remains were sucked into the portal. Indy, Marion, Mutt and Oxley found their way out above the valley of Akator, and observed the temple collapsing, revealing a huge flying saucer which vanished soon after.

Appearances

 * Indiana Jones and the Infernal Machine
 * Indiana Jones and the Kingdom of the Crystal Skull