Only souls who weighed exactly the same as the feather of the goddessMa'at were allowed to start a long and perilous journey to Aaru, where they would exist in pleasure for all eternity. The ancient Egyptians believed that the soul resided in the heart. Those whose heart did not match the weight of the feather of Ma'at due to their sins were excluded. They were said to suffer a second death when devoured by another being, Ammit, while still in Duat for judgment.
The souls who did qualify had to undergo a long journey and face many perils before reaching Aaru. Once they arrived, they had to enter through a series of gates. The exact number of gates varies according to sources; some say 15, some 21. They are however uniformly described as being guarded by evil demons armed with knives.
Aaru usually was placed in the east, where the sun rises, and is described as eternal reed fields, very much like those of the earthly Nile delta: an ideal hunting and fishing ground, and hence, those deceased who, after judgment, were allowed to reside there, were often called the eternally living. More precisely, Aaru was envisaged as a series of islands, covered in "fields of rushes" (Sekhet Aaru), Aaru being the Egyptian word for rushes. The part where Osiris later dwelt was sometimes known as the "field of offerings", Sekhet Hetepet in Egyptian.