Maya

Maya was the Elemental Master of Water, the wife of Ray and the mother of Kai and Nya, the latter of whom would inherit her abilities. Maya fought alongside the other Elemental Masters and her husband in the Serpentine War, which would see the people of Ninjago fighting the Serpentine. Eventually, the Serpentine were sealed away in various tombs. What became of Maya and her husband following the war is currently unknown, though their children would go on to become skilled Ninja and masters of Spinjitzu.

Spellbound (flashback)
As the Elemental Master of Water, Maya was a member of the alliance of the Elemental Masters during the Serpentine War. She fought along several other powerful masters to fend off the Serpentine attacking Jamanakai Village though was forced to retreat when the Anacondrai arrived.

The Master of Water marched into battle with the alliance against the Anacondrai in Birchwood Forest, but due to Chen's manipulation, the Masters turned against each other and the battle was lost. Eventually, she helped win the war by using a Sacred Flute to lock the Venomari into a tomb in the Toxic Bogs.

She later married the Elemental Master of Fire and they had two children; Kai and Nya.

Dark Island Trilogy, Part 3
Following an adventure on The Dark Island, Wu had a vision of Maya and her husband in the present, apparently being forced to forge something in a shadowy pit.

Appearances

 * 70627 Dragon's Forge

Season 4: The Tournament of Elements

 * 40. "Spellbound"