What did the earl of kent do to serve his king and to save his master?
Kent sacrifices his privilege, status, and identity to serve Lear. Kent disguises himself as a beggar/servant, Caius, to save his master:
Lear asks, "This is a dull sight. Are you not Kent?"
Caius (Kent) travels with Lear, protecting him. He is a kind of seeing-eye dog (guide), who is fiercely devoted to his King and master. He knows that Lear will regain his senses, that the King is merely grieving and disoriented.
When crazy, Lear tells Kent, "Follow me; thou shalt serve me: if I like thee no worse after dinner, I will not part from thee yet. Dinner, ho, dinner! Where's my knave? my fool? Go you, and call my fool hither.
But, even though Lear never praises him for his loyalty, Kent even follows him to the death.
Kent says at the end: "I have a journey, sir, shortly to go; / My master calls me, I must not say no."