The Ma'at, sometimes also called Maat, is the cosmic principle of virtue, justice and balance that perpetuates the world.
The Amenti and their predecessors, the Shemsu-Heru, adhere to the strict tenures of the Ma'at in order to be seen as worthy before the Judges of Ma'at to be blessed with resurrection. Certain actions (such as lying, murdering and addictive behaviours) are violations of the universal principle of justice. As agents of Ma'at, mummies are expected to avoid such transgressions. Failing to uphold the balance can result in the inability to advance in understanding of the divine principle.
The road of Ma'at is a difficult one to walk, and not all of the Reborn can make the journey. The world of the living is filled with temptations, some of which are created by agents of Apophis and others of which are simply a part of being alive. Mummies possess immortality, sensitivity, mystical power, and a first-hand understanding of how precious life is. Although they have been a keen appreciation for Ma'at, they often face a greater temptation to abuse the gifts that they've been given.
Some of those who succumb become Bane mummies in the service of Apophis, others are cast down to Amemait. The individual attunement of a mummy to Ma'at is measured in Balance. In modern times, Ma'at is threatened by Apophis and his minions who strive to topple the balance completely and they seem to be very accomplished in this goal. Mummies are expected to fight against the harbingers of corruption and restore the balance to its proper place.
The Followers of Set also use the term Ma'at to refer to the chains the Aeons placed upon all living souls to keep them subservient to them and entangled in the illusions of the material world. Ma'at is seen as a force of ultimate stasis that strives to imprison mankind into the base world of matter, denying them their true potential. The Setites break these chains through the Gates of Revelation, through rage, lust, ambition and desire that eventually lead to gnosis.
In the Dark Ages, this belief slightly differed. Ma'at was seen as the balance between life and the afterlife. Each world mirrored the other until Ra and Osiris unbalanced Ma'at with the creation of law. The Followers of Set sought to return the balance of Ma'at by disrupting society's disproportionate influence.
The idea of Ma'at and its place within the cosmos shares some similarities with the being called Gaia that the Fera revere. They believe that Ma'at was once expressed in the symmetry of the Triat, before it became unbalanced.