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The lowdown on creatures one may encounter:
Free Magic constructs: very similar to Charter sendings (though considerably more aggressive), or worn by Free Magic elementals or power dead spirits. Free Magic constructs are usually formed from a mixture of dead animals and inorganic matter. One such creature was made from "Free Magic and the flesh of swine." Another example is a Ferenk, ancient Free Magic scavengers that wear bodies of stone and mud. Though such constructs may be destroyed under certain circumstances, destroying the Elemental itself is much more difficult and typically the province of Free Magic.
Free Magic Elementals: These free-willed beings are wholly composed of Free Magic. The most common elementals belong to specific "breeds" (such as Stilken, Margrue, Jerrek, or Hish), while the most powerful are unique, or "of a singular nature". Though "many thousands" of Free Magic Elementals escaped the creation of the Charter, most were later bound or made to serve. Of the remainder, "no truly dangerous creature of Free Magic has woken in a thousand years, save to the sound of Mosrael and Saraneth, or by a direct summons using their secret names." Elementals are difficult to deal with, as some cannot be destroyed except by a Free Magic sorcerer more powerful than they, or by immersion in running water (though Free Magic creatures of the Third Kindred, or those infused with the essence of the Nine, are exempt from this rule). Charter Magic is typically ineffectual: the power of the Charter is in binding, not destruction, and each Free Magic being must be bound in a specific way. It takes no fewer than three master Charter Marks to bind a Stilken, and these are so powerful that they are individually lethal to an unsupported Charter Mage.
Charter Sendings: Charter Sendings are servants or sentries constructed entirely from Charter Marks. They are not completely free-willed: many may only act within the limits of the purpose for which they were made. Certain fixtures excepted (such as a surcoat or insignia), Charter Sendings do not possess a concrete physical shape. Charter Sendings derive identity primarily from their function, though they are not incapable of developing a personality. Charter Sendings are capable of emotive response, but they are not free agents: they are created to be willing servants of the Charter.