Each of the @Endless has a realm in which they are absolute sovereign. Within their realm, all members of the Endless have a "gallery" containing symbols or sigils of the other Endless. The Endless may contact each other by holding the appropriate sigil and calling for that member of the Endless.
Within these galleries, each of the also possesses a sigil, though it is not necessary to hold the sigil when you speak to another Endless; it seems to be customary to hold it, tell your sibling that you hold their sigil, and then ask permission to enter their realm or call them into yours. The @Sisters of Fate are also able to summon their siblings by using the @Mirrors of Destiny, whether they want it or not. As shown with @Morpheus and @Akhlys, it is possible for each of the Endless to contact the other Endless without necessarily holding their sigil or even being in the gallery.
It is known that the Endless are not to be seen as gods: while gods need to be believed in to exist, The Endless will continue existing whether we believe in them or not, for they are The Endless.
The Endless spend most of their time fulfilling their functions as embodiments of natural forces. However, some of the Endless are more dedicated to their tasks than others. If one of the Endless is destroyed, then he or she will be replaced by another aspect of their role, but this does not occur if they are simply absent or inactive. In such cases, the aspect of existence supervised by that member of the Endless becomes more random and chaotic. During this time, the universe may attempt to replace that member by putting some of their essences within a mortal.
In reality, each Endless is really a lord of opposites: life and death, dreams and reality, destruction and creation, destiny and freedom, desire and hatred, despair and hope, and delirium and sanity.
The Endless seem to have some rules regarding the way they experience their existence with some definite taboos if they wish things to go as they would prefer. Breaking these rules will bring great consequences upon the Endless who does so, including total destruction by the @Furies.
Harm will befall anyone who has hurt their family.
Do not fall in love with mortals or the mortal's downfall is assured.
The Endless cannot take a mortal life unless they become an active threat to themselves and their realms.
Respect roles and domains.