The Kingdom of Maru is an ancient kingdom whose people harnessed the most ancient and powerful magic in the world which is stored in the Codex Maru. The sorcerer priests and priestesses of Maru created all sorts of magical artifacts such as the Amulet of Avalor, the Eye of Midnight, and the Scepter of Light from magic crystals grown in the Mystic Isles by Crystalmasters on the Isle of Crystals. According to Zuzo, they made all sorts of magical objects. Because they wanted their magic to be used for good, they also gave some of their creations like the Amulet and the Coza Kex Curse Unleashing abilities that activate when bad deeds are made. It was a wizard from this kingdom who imprisoned Orizaba in the Spirit World. One day, Maru vanished without a trace, and the Kingdom of Avalor rose in its place. According to Mateo, no one knows what happened to them.
The architecture of Maru appears to be based on the Yucatan Mayan Pyramids as they too lie in ruins, and as stated by the Mateo, the Maruvians disappeared without a trace, the same as for the Mayans.
In the season two premiere, "The Jewel of Maru" Elena learns from the ghost of the last Royal Wizard of Maru, named Amalay, what happened to the Maruvians. Shadow spirits attacked the Maruvians and they used the Jewel of Maru, their most powerful magical gem, to drive them back. Unfortunately, the great power used by everyone had the effect of a magical atomic bomb, sending everyone to the Spirit World. Amalay's ghost remained to guard the Jewel of Maru until it could be safely sealed away forever. Once Elena succeeded in doing so, Amalay departed to join the rest of the Maruvians in the afterlife.