The Zeta Dragon is the fusion of all the namekian dragons (Shenron, Porunga, Black Star Shenron, Black Smoke Shenron). The result was massive. Due to the dragon's dramatic increase in power, it was now independent, meaning if the creators of the individual dragons had died, it would not affect the existence of the dragon. After the big collide, the new dragon was granted new powers. It could now grant five wishes at a time, it can also make any wish no matter what it is. For example, the dragon can wish away strong enemies like Omega Shenron or Majin Buu. The dragon can even spawn previous enemies into new entities.
The Zeta Dragon appears as a pure grey dragon with red spikes. It also has green eyes instead of Shenron's original red eyes.