Xu Kai is the current leader of The Sun by choice, and by birth of the green dragons (largely based in the Eastern hemisphere). He’s old and wise (as one might expect), and fairly brave. Most of the green and yellow dragons hid underground centuries ago, but not Xu Kai.
He is also considered leader of the dragons until Suvi comes of age, giving him the title of Peak.
His ability to heal is unparalleled, even among most members of the Sun, so no one complained when he chose to identify himself as a citizen of Zenith.