The Tribe of Ancients were an advanced civilization appearing in Super Paper Mario that was led by four sages, including Merlimbis, a female sage that created the Pure Heart, Merloo, a male sage that wrote the Light Prognosticus to counteract the Dark Prognosticus, Merlight, another male sage that designed Flipside, and Merlumina, whose spirit guarded the Pure Heart in Yold Desert for 1,500 years.
The ancients studied and believed strongly in the power of love (and therefore had rather wild romance relationships). They traveled to many worlds to share this belief and entrust people with Pure Hearts, the eight parts of the Purity Heart. The Pure Hearts were drawn by their own power toward those strong with love. The Ancients used this trait to find suitable guardians in each world. Many of the Ancients who found guardians fell in love with those they met. They ended up living their days happily in the world they'd visited out of duty. This is how the legend of the Hero was passed down from generation to generation.
The Ancients were wise, but they lacked physical power. They needed strength. For this, they created the Pixls for any manual labor they could not do themselves. With the help of the Pixls, the Ancients made amazing worlds.
The Ancients then created Flipside. However, Flipside was losing stability. When they came to the realization that for all light there must be dark, they created Flopside with help from the otherwise isolated Tribe of Darkness, who were once members of the Ancients. Flopside's darkness is the reason for Flipside's stability and longevity. The Tribe of Ancients also locked Wracktail in the Flipside Pit of 100 Trials, and Shadoo in the Flopside Pit of 100 Trials.
Their power and influence declined, however, after the Pixl Uprising.