The Kamidogu of the Mortal Kombat universe are mystic relics crafted by the Elder Gods which are said to contain the essence of the realms. When used in sorcery, they are said to have incredible power. Wielded in the wrong hands, the Kamidogu could endanger existence itself.
The Kamidogu embody the essence for each of their respective realms. Of the six Kamidogus that Shujinko collected in his quest during the events of Mortal Kombat: Deception, there was one pertaining to each realm: Earthrealm, Netherealm, Chaosrealm, Outworld, Orderrealm, and Edenia.
Representing the essence of their realm, the appearance of a Kamidogu reflects the nature of its respective realm. The Kamidogu of the Netherealm has an appearance that is visibly sinister. The Kamidogu of Edenia likewise, has a more serene look to it. When Shujinko was in possession of them, he was able to travel freely between the portals of the realms, by way of accessing the Nexus.
The Kamidogu and Shujinko's Quest
The Kamidogu were introduced in Mortal Kombat: Deception and were the foundation of the story. More precisely, when playing Mortal Kombat: Deception's Konquest Mode, the player assumed the role of Shujinko in his quest for the Kamidogu.
Decades ago, Shujinko, as a child was approached by a ethereal spirit entity that called itself Damashi. Damashi claimed to be the agent of the Elder Gods who was charged with finding a mortal who had the courage and potential strength to undertake a quest for the Elder Gods. Shujinko, then only a child, eagerly accepted and Damashi charged him with gathering the six Kamidogu of Earthrealm, Netherealm, Chaosrealm, Outworld, Orderrealm, and Edenia. To aid Shujinko in the quest, Damashi mystically instilled in Shujinko an enhanced ability to observe and then wield the Kombat abilities of warriors that he came across.
However, in reality, Damashi was not an agent of the Elder Gods. Ages ago, the Dragon King, Onaga,was slewn by Shao Kahn. But, even from the void, his essence could extend into the realms. Damashi was actually only Onaga's essence, extending into the realms. Thus disguised, "Damashi" was able to manipulate Shujinko into undertaking a quest to collect the Kamidogu.
Onaga, having acquired the Kamidogu, traveled to re-assume his throne as the original ruler of Outworld. From there, he intended to use the Kamidogu to attain ultimate power by unmaking the realms in his image.