Eidolon

Eternal Guardians

To describe what an Eidolon is can be a difficult thing for most to grasp, a basic knowledge of one will refer to the bodies that they possess in order to act as guardians or sentinels over a place or area. These are often known as Eternal Guardians as well. This does not begin to define what an Eidolon actually is, for what the core of an Eidolon is, is not the same as the bodies it inhabits when in physical planes.
The core of an Eidolon is a creature, both an outsider and a construct of thought or belief. In this regard, they are similar to Eikons, though the prevailing belief is that an Eidolon is a failed Eikon, either not enough belief or power was used in its creation so it forms into the essence of an idea. A few significant differences between the two is the power of the being and how difficult they are to summon. Where an Eikon is only as powerful as the amount of power given to it during its creation and summoning an Eidolon's power is formed on its essence and the body it is given to inhabit.
An Eidolon is summoned into an anchor, or phylactery as a means to hold it to the plane it is called to. Inside this anchor is a figurine that is made in the form the Eidolon will inhabit, the size can vary of the Eidolon with various empowering or restraining runes on the figure. The body will form upon binding the Eidolon to the anchor made of the same material used to fashion the figure and in the same shape and design. More elaborate figurines can be enchanted to also bestow powers onto the Eidolon's form, an example being one made into the shape of a dragon would not have a breath weapon, unless enchanted in a way to have that.
Regardless of the form the body takes the Eidolon is not one of that creatures, an Eidolon made out of bone is not Undead, the bodies are constructs, the essence outsider. While an Eidolon is bound to an anchor it can not be banished until the anchor is destroyed. Should the body be destroyed a new one will form in time, this process can be accelerated by having an abundance of the same material used for the body around.
The term 'Golem' is one that has blurred into the territory of Eidolon as well, only those with an understanding of the nuances between the two can easily tell the differences. Some of those differences are golems are animated by elemental beings bound to a body and once destroyed the elemental returns to where it came from. A golem will only do what it was told to the best of its ability, an Eidolon has a purpose and an at least partially formed identity that enables it to think and react to achieve its objective. Eidolon's after their creation and possession of a body can freely enter areas of wild or null magic without becoming immobilized, though magical abilities will still be affected. Golems are used more for creating Striders or Airships as they make effective power sources that can't exert their wills on the vehicle against that of the pilots. An Eidolon could be bound to such a machine but it will do as it sees fit and must be treated more as a companion than a vehicle, there is some benefit to this though as they are able to extend their abilities across their forms such as regeneration or the ability to fight. This was attempted in the Dark Ages by binding an Eidolon to an entire keep that was going to be used in an assault of Etrisium, the Eidolon was not strong enough to move its body by itself and so was empowered by elemental crystals of great power. The fortress itself was infiltrated during the battle and those crystals were removed causing the Eidolon to come to a halt later the anchor was destroyed sending the Eidolon back from whence it came.