The six Kamidogu that embody the essence for each of their respective realms.
Concept art of the Kamidogu.
The Kamidogu (from Japanese kamidōgu 神道具 literally "god tool" or "divine equipment"), 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 that can make and unmake all of reality. The Power of each Kamidogu can only be fully used by one Individual, so if one were to make use of all the Kamidogu, this person has to fuse all six Kamidogu into One Kamidogu. Wielded by the wrong hands, the Kamidogu could endanger existence itself.
The Kamidogu embody the essence for each of their respective realms, and there is one pertaining to each realm: Earthrealm, Netherrealm, Chaosrealm, Outworld, Orderrealm, and Edenia.
There is one more Kamidogu that is connected to and surpasses all the other Kamidogu as it embodies the essence of not just one realm, but all of the universe. That final Kamidogu turned out to be the Sacred Amulet which is the Amulet of Shinnok.