Aetherium

A strange world inhabiting another dimension, the Aetherium was ruled by and alien warlord named Marduk. It consisted of otherworldly machinery and a gaseous substance any person can swim through as if it were water.

The realm was connected by various portals between it and Earth. Marduk made contact with the ancient Babylonians who accepted him as their chief deity. Marduk commanded the Babylonians to construct the Infernal Machine which will enable him to travel to Earth and claim it as his own.

After Marduk's demise at the hands of Indiana Jones, the Aetherium self-destructed and vanished forever.