Round Table

It is not uncommon for kings to create their own council of advisors to help them lead their country effectively. The newly crowned king of Avalonia has elevated that into something special. The knights of the Round Table is a collection of the most powerful people in the land, gathered for their unique skills and having succesfully defended the kingdom against all kinds of dangers; sitting around in the same room, at the same table (hence the name), all as equals no matter their background. The king didn't want to differenciate the literate and those who are not, the rich and the poor, the noble from the commoners - the only criteria is to have the kingdom's best interest at heart and proving that in action. It is true however, that the rich can afford better armour, the literate can learn how not to let the dangers get to them too close and the noble have the proper connections to find out all sorts of other useful things. It would be foolish to think that everybody in the kingdom has the opportunity to join them, but many people still dream about it. Few of them succeed. You might be one of them.
There are only limited seats available and that is reflected by the state of the kingdom. The more prosperous your land is, the more seats are available. It does not mean that the king is equally as powerful but most often these two things correlate, because only the king can accept a new knight into the group. There has never been an instance of a knight being kicked out of the group, but then again their lifespan doesn't tend to be very long, in these harsh and dangerous times. 
The knights of the Round Table are supposed to lead by example. They weild enormous power and should inspire noble ideas wherever they go - all in the name of serving the kingdom. That often means being on the front lines whenever something dangerous happens, or, should they not be the fighting types, right in the heart of a problem, where one might get easily poisoned, cursed or driven insane. For that they command a great deal of respect among the common people.
Round Table should not be mistaken for a personal guard of the crown. Not by the people and not by the royals either. "Serving the kingdom" may be interpreted in many ways.