The Five Harmonious Ones
Five immortal spirits who originally created the zodiac spirits. Each guard a point of the compass and represent one of the 5 classical elements of Ancient China.
Xuan Wu the Black Turtle- Guardian of the North, wielder of the attribute of Wood. Creator of the Rat, the Ox and the Pig.
Biahu the White Tiger- Guardian of the West, wielder of the attribute of Metal. Creator of the Dog, the Monkey and the Rooster.
Zhuqiao the Vermillion Bird- Guardian of the South, wielder of the attribute of Fire. Creator of the Horse, the Goat and the Snake.
Qing Long the Azure Dragon- Guardian of the East, wielder of the attribute of Water. Creator of the Rabbit, the Dragon and the Tiger.
Huanglong the Gold Dragon- Guardian of the Centre, wielder of the attribute of Earth. Creator of Xuan Wu, Baihu, Zhuqiao and Qing Long.
Huanglong can only exist if two of the opposite Spirits (e.g. Xuan Wu and Baihu) combine. The strongest form of Huanglong is created when all four other spirits combine. Huanglong can also come into existence if all twelve zodiac spirits combine.
(Just for the record, we need a tortoise or turtle in the companion set)