The Core was the name for the magical 'world' within 6664332. It was the hub of the worldwide Golem Network. Beings from the real world get transported into the Core, where they are termed Wielders. The first Wielder to enter the Core in thousands of years was Tobijah Kruel, now the Void God. He had influence over the Core's system and later assumed direct control of the golem. Following him were Relfthra, Amarian Zeshuwal, Bobby "Caps" Locke, Korrin, Jammal Hildebrand, Ianthe Marsh, Voldana, Masked Assassin and Kraus Gardham.
The Core in inhabited by two types of creatures; Souls, beings who were sacrificed long ago to forge 6664332, and Enchantments, the sentient magics employed in the golem's creation and programming. After the countless years together, the difference is minimal.
The Void God, or KRUEL as the Enchantments referred to it, began converting Souls and Enchantments into Guards, extensions of KRUEL's will that could permanently assume control of any golem in Azeroth.
The Core had two main parts: Core City, where the Souls and Enchantments lived; and the Arena, where they were set to fight to the death for the amusement of others. KRUEL began to use the Arena to determine the best to convert to Guards. The Wielders exploited this to get access to central command and destroyed the Core.