The climax is when Richard gives his speech in Act III about being king and when he talks about death and graves.

What is x?
Richard II is x and while he is king of England, he is pretty pathetic. He is confused and is at his wits end with knowing how to run his country and control the people around him.

What does x do?
He is king, but not for much longer. He can tell that his eventual overthrow is inevitable. He compares giving up his crown to committing suicide, since he is sanctioned by God to be king.

What does x mean?
It means that there will probably be war to gain control of the country and there will eventually be a new king, Henry.