The Elemental Creatures were born as Okoto came into being, each born from a different element that made up the island. In response to their creation, the Shadows gave birth to Umarak, who's sole purpose and intent was to hunt and capture the Creatures.
Even before the time of the Mask Makers, the Okotans knew of the Creatures, having named their six regions after them (with the exception of Agil), and had produced many carvings of them. The Creatures foresaw an imminent cataclysm, they were unable to prevent it but aimed to prepare for it. All of the Elemental Creatures, except the Creature of Light, appeared before Ekimu during the Festival of Masks. This led Ekimu Ekimu to don the Mask of Time, to see what the future held. After he learned of the coming of the Toa and that they would need Golden Masks of Power, Ekimu received an Elemental Crystal from Uxar. Ekimu then sent the Protectors to retrieve the other Crystals from the remaining Creatures.
After the Toa recieved new armour and masks from Ekimu, the Toa received visions of the Creatures and later set out to find them at their respective temples in each region. In different ways the Toa realised they had to work as equals with the Creatures, which enabled them to obtain their Golden Masks of Unity and unite with the Creatures to gain additional powers. Together they all travelled to the Labyrinth were confronted by Umarak, who used Ketar as leverage to steal the Mask of Control. Pohatu was able to save the Creature by overcoming his fear of scorpions.
When they reached the Ancient City of the Mask Makers, it was soon attacked by Umarak's Elemental Beasts, prompting the Second Battle of the Ancient City. Together with the Toa, the Creatures defeated the first wave of beasts and stayed behind to continue defending the city when the Toa departed to destroy the Mask of Ultimate Power as well as prevent Makuta's return. The Toa were later joined by Agil, the seventh Creature.
(It is unknown whether Umarak qualifies as the eighth Elemental Creature, since he is the Creature of Shadow, but has not been referred to alongside the other Creatures)