The Hand of the King or Hand of the Queen, in cases of a ruling female monarch, or simply the King's Hand, is the most powerful appointed position in the Six Kingdoms, second only to the King in authority and responsibility
"The world hadn't seen a dragon in centuries until my children were born. The Dothraki hadn't crossed the sea. Any sea. They did for me. I was born to rule the Seven Kingdoms, and I will."
―Daenerys Targaryen to Jon Snow