Great beings of the Tongxuan Realm, even if their physical bodies perish and their Primordial Spirits are annihilated, as long as their most core, most vital True Spirit remains, can reincarnate anew.
During reincarnation, the True Spirit absorbs some energies from the unknown, and then re-cultivates a soul. In this process, the True Spirit gradually becomes veiled with mortal dust.
Therefore, after great beings of the Tongxuan Realm are reincarnated, they need to unravel the mystery within the womb, so that the veiled True Spirit may regain its glory. Only then can they recall everything from their past lives.
The True Spirit is the most essential and crucial entity for those above the Tongxuan Realm, with all memories within the Primordial Spirit backed up within it, including one's innate talent; upon breaking the mystery within the womb after reincarnation, all that is stored within the True Spirit will be restored.