In the TV series The Shannara Chronicles, there has been the reference to Four Lands on many occasions. They have been called as Northland, Southland, Westland, Eastland according to the books by Terry Brooks. Who are the rulers of these lands in the TV show? The lands are inhabited by different kinds of creatures like Gnomes, Trolls, Humans, and Elves.
This is somewhat complicated, and as far as I know needs to be answered from the books.
The Westland is controlled by the Elves, who are are ruled by King Eventine Elessedil. They are the only unified kingdom.
The Southland is mostly ruled by the Federation, which is more of a council and does not have a king or any person on it that you ever hear. The exception is the borderland Kingdom of Callahorn, who after the the Third war of the races saw themselves as apart from the Southland. Smaller kingdoms like Leah were annexed.
The Eastland is ruled by the Dwarven Tribes in the southern Eastland, and the gnome tribes in the north Eastland. They are constantly at war with each other. The Dwarves should have a king that would have followed Raybur, but I don't believe one is ever actually mentioned. As mentioned below the gnomes are fractured from the last war.
The Northland is fractured, it is the home of the Trolls and some of the gnome tribes. At the time of the show it is extremely chaotic, as that was where the Warlock lord attacked all the other races from about 30 years before the show starts, and the Trolls and the Gnomes who fought with him are now in disarray, and shunned by the other races. See The Four Lands
Only the Elf King could be said to be the King of the Westland. No other race or land has a unified leadership, though smaller tribes/countries may have a leader they consider a "king".
The Four Lands should make it clear that these are geographic, not political divisions.