Malchus

In Kabbalistic terms the sphere (and Sfira) in which we humans operate is called מלכות, Malchus. Malchus means monarchy, and this begs the question: What does Monarchy have to do with our sphere of activity?

The Gaon of Vilna explains that the primary function of Creation is for us to find the presence of God in Creation. Ultimately, it is our mandate to discover the God permeates the entirety of Creation, as much as that doesn't seem to be the case to the naked eye at the present time.

The concept of Monarchy demands that there be only one monarch and not more (אין שתי מלכים משתמשים בכתר אחד). God created all the forces that appear to oppose Him in order for us to ultimately come to the realization that there is no other. It is our activity in bringing about this revelation, that gives the name Malchus to our sphere.

Hashem Needs You

Despite the fact that Hashem is perfect and needs nothing from Creation, He created the illusion that He needs our assistance. Hashem created the world in an imperfect manner and left it up to man to perfect His Creation. The arena is which this perfecting is done is referred to in Kabblah as מלכות (Malchus, monarchy), the tenth and final Sefirah.

That which is done in Malchus is for Hashem's sake.

Malchus is different than the traits represented by the other Sefiros. A person can be a Chacham (wise) without there being someone lacking in wisdom. A person can be a גבור (strong) without there being someone who is weak. These are traits which are inherent within a person that have no relationship to anything external.  Being a monarch, by contrast, can only be true if there is someone over whom to rule who accepts that rule. There can be more than one wise or strong person, but there can be only one king.

It is only with the cognizance that one is serving within Malchus, that one makes Hashem into the monarch.