Primordial Consciousness

The Primordial Consciousness (also known as the Primordial Mind or Primordial Origin ) is the first mind to exist in the lore of Dota 2, long before creation and existence itself.

Lore
It is said to be the progenitor of all creation, at least according to one of its greater fragments. When the universe was created, it was split into many fragments. Three of its greater fragments were known as Radinthul, Diruulth, and Zet. Because they all share the same progenitor, Zet sometimes refers to its sibs as its other selves, as if they were one and the same being.

The two greater fragments of the Primordial Mind (now known as the Ancients) exist in the Nemesis Stones that once made up the Mad Moon before it was destroyed by the warring Ancients. On the other hand, the power that Zet used to imprison them both was trapped in a stone known as Nemestice, which also dwells in the same moonstuff that once formed the Mad Moon.

Arc Warden states that this mind and its fragments (including himself) existed in a world before the current world. It is unknown what this world is called.

Speculation
The lore about the Wailing One sounds very similar to the lore surrounding the entity known as Zet. Although both stories have their differences, they both mention a primordial mind that predated all of existence and was subsequently shattered to witness all of creation. Both stories even mention a great schism.