Gali was one of the toa, great spirits tasked to protect the island of Mata nui, from the evil Makuta. She is the spirit of water.
Gali is the water toa and as such can control and produce water. If her water powers are used to much at one time they can be exausted but she can recharge by absorbing water. Gali wears the Great Kanohi mask Kaukau, which gives her the ability to breath underwater. She also wields two large hooks as weapons and for climbing. Her body is made of protodermis, an extremely hard biometal. A form of her water powers allows her to heal others.
Gali was a member of the toa team including Tahu, Pohatu, Onua, Kopaka, and Lewa. They arrived on Mata Nui unaware of who they were. They found villages of beings called Matoran who had awaited their arrival to free them from the tyranny of the Makuta. The Matoran were led by wise beings called the Turaga who knew the toas' names and purpose. It was their destiny to find all of the great Kanohi masks and use them to defeat Makuta who had polluted the minds of the animals of Mata Nui, known as Rahi, and put the Great Spirit Mata Nui to sleep. Tahu became the leader of the team.
In their first journeys throughout the island Gali gained five other masks aside fromm her mask of underwater breathing. They gave her the powers of shielding, x-ray vision, super speed, super strength, and levitation. At the temple Kini Nui the six masks were combined into one golden mask that allowed him to use all of his mask powers at once.
The toa descended to the deep tunnels of the island where they faced shadow versions of themselves, created by the Makuta. They were victorious and reemerged and finished reverting the Rahi to normal.
The toa later faced the threat of the Bohrok swarms, mechanical bugs that functioned as suits for the Krata. The toa gathered one of each kind of Krata and used them to unlock and activate the exotoa, power suits of armor. They then used these suits to battle the Barahg twin queens. At the end of the battle they took off the armor to unite and use their combined power to imprison the Bahrag. The resulting energy burst threw them into pools of energized molten protodermis transforming them in to the toa nuva.
As a toa nuva Gali gained greater control of her water powers. Her hooks were turned into two large axes that resembled fins and could be worn on her feet for swimming. There were propellers on her wrists. Her golden mask lost five of its powers but it kept underwater breathing and it could now extend its power to those around it.
Shortly after, the Bohrok kal attempted to free the bahrag. The toa battled the bohrok kal underground. They were able to stop them when Tahu nuva slowed down time. It gave the others a chance at getting past the bohrok kal's defenses and they failed to revive the bahrag.