In order for a host to conjure ones Will and influence the world around themselves they must declare an Edict. An Edict is a proclamation one gives to the world around them and their Will does/attempts to achieve it. If the Edict succeeds whatever effect the host wanted happens, if the Will is not strong enough to achieve it, the host made a poor Edict, or its rendered impossible to accomplish the Edict fails and the Will spent is wasted. Edicts very from person to person as each soul is unique. What would be simple for one Host can be extremely difficult for another and accomplishing the same task can vary extremely from person to person. Through practice and self reflect, a Host can learn many Edicts but their specialty lies with their Sovereigns.
Sovereignty aka Sovereign
A Sovereignty is supremacy over something. A hosts sovereign is what edicts they are most effective at casting, either though practice or natural talent. For example, sovereignty over fire would have the host extremely effective at manipulating fire with their will. Having sovereignty over one aspect will make the opposite aspects more difficult to conjure however.
A gatekeepers domain is apart of their Sovereign. The domain means how much and how far ones Will can manipulate things around them. Using will to change something outside of ones domain, either skillset or distance, drastically reduces its effectiveness.