Tribe of Ancients
The Tribe of Ancients were an advanced civilization spoken of by various characters in Super Paper Mario. They were highly intelligent and possessed great magical power, and their influence spread across many dimensions for thousands of years. The Ancients' counterpart was the Tribe of Darkness, which splintered off from the rest of the Ancients 2,000 years prior to the events of Super Paper Mario. While the Tribe of Darkness kept to themselves and forbade marriage outside their group (for fear of diluting their magical powers), the Ancients had great faith in the power of love, and the passion of some became the stuff of legends. 1,500 years before the events of Super Paper Mario, a particular group of Ancient sages created the Light Prognosticus to counteract the grim prophesies of the Dark Prognosticus (whether this book was written by an Ancient as well is unknown); they also constructed Flipside, and saw to the distribution of the Pure Hearts across the land, believing that the power of love would be the only way to save the universe from the destruction foretold in the Dark Prognosticus.
The ancients were an incredibly intelligent race that possessed powerful magic, however they lacked physical strength. 3,000 years before the events of Super Paper Mario, one of the Ancients circumvented his race's physical limitations by creating the "thinking tools" known as Pixls using knowledge gleaned from the prophetic book, the Dark Prognosticus. The Ancients used the Pixls to build great cities and spread their knowledge across many worlds. However, they grew dependent on their living tools, and after 1,000 years of prosperity, they were devastated by the uprising of their Pixls, who had fallen under the control of an entity called the Pixl Queen. The Pixl Queen had been the first Pixl created, and was horrified at how her fellow Pixls were being used, but her revolution was eventually foiled by the twelve original Pixls (besides herself) and their Ancient partners, all but one of whom perished.
The survivor discovered that the Pixls had been created from the souls of deceased people (with the Pixl Queen in particular being the daughter of the Ancient who made the Pixls), and to prevent the knowledge contained in the Dark Prognosticus from being used in such a way again and causing another tragedy like the Pixl uprising, he took the book and disappeared. He later founded the Tribe of Darkness, a group of Ancients who became known for their great power and secrecy. The Tribe of Ancients accused them of stealing the Dark Prognosticus, and the idea that they wanted to use the book to enhance their shadowy powers joined the true story of their shielding of the book from those who would misuse it.
Five hundred years after the Pixl Uprising, the Ancients became aware that the Dark Prognosticus predicted that all worlds would be consumed by a Void in 1,500 years' time. A group of four sages believed that the power of love could prevent the destruction, and their research led the construction of the Purity Heart, which was meant to destroy the Chaos Heart that would create The Void. They wrote another book called the Light Prognosticus to provide the destined Heroes of Light with instructions and guidance in how to prevent the consumption of all worlds, and broke the Purity Heart into eight smaller Pure Hearts, which they then passed out to other trustworthy individuals for safekeeping for the next 1,500 years. They also created Flipside, a world between dimensions, and with the help of the Tribe of Darkness, they created its dark counterpart as well, Flopside, and hid Heart Pillars around both cities so that only the hero would be able to go to them and deposit the Pure Hearts. They also used the Flipside Pit of 100 Trials to research the power of the Pure Hearts, while the Flopside Pit of 100 Trials was used to study the dark magic of shadows, with both also serving to test the forces that guarded the Pure Hearts.
However, the Ancients' time was limited. After the Pixl Uprising, the Ancients grew fearful of their "thinking tools". They outlawed their creation and limited the power of the existing Pixls, which slowly dwindled in numbers until only the original eleven Pixls (down from twelve, as one died defeating the Pixl Queen) remained, scattered across the worlds and hidden in Treasure Chests to await the Heroes of Light. Without the Pixls, the Ancients' power and influence began to decline, and by the time the events of Super Paper Mario began to play out, their civilization was all but lost. Only a few descendents of the Tribe of Ancients are encountered in Super Paper Mario, as well as the last member of the Tribe of Darkness and the lingering spirit of Merlumina, one of the four sages.
A few Ancients are spoken of in Super Paper Mario, namely, the four sages (see below). Numerous descendents of the Tribe of Ancients and the Tribe of Darkness are also encountered, including Merlon, Merlee, Merluvlee, Bestovius and Old Man Watchitt and his grandson Bozzo (all descendents of the Ancients), as well as Nolrem (a descendent of the Tribe of Darkness). Count Bleck is the last remaining member of the Tribe of Darkness, although his father was also involved in the backstory between Bleck and Tippi.
 The Four Sages
Merlimbis, who is described by Tippi as "gentle and loving", was one of the four sages among the Tribe of Ancients. She is thought to have created the Pure Hearts, and therefore the Purity Heart. She is never directly met, only viewed in a stained glass window in Mirror Hall, which reveals that she looked very similar to Merluvlee and Merlee, both of whom are direct descendents of Merlimbis according to Tippi and Tiptron.
Merlight is revealed by Tippi to have been quite knowledgeable in the nature of Dimensions/worlds, and used this knowledge in the design of Flipside. He is distantly related to Merlon, who looks identical to him and apparently possesses a large amount of the books Merlight left behind. However, the angular positioning of his hood in the stained glass window of Mirror Hall he is seen in actually makes him appear somewhat similar to Merlon's appearance in Paper Mario: The Thousand-Year Door, though this may be a coincidence.
According to Tippi, Merloo was very wise in his time and is even thought to be the author of the Light Prognosticus (although authorship is also credited to Merlumina). He has the appearance of a mustache-less, green-robed character, but while the other sages look very similar to the "Shaman" character encountered in the game, Merloo only bears a passing resemblance to Merlon and Nolrem. However, Merloo is said to be a powerful, dimension-controlling magician, which is similar to the "Flip Wizard" Bestovius, a descendent of the Ancients (and possibly Merloo) who gives Mario the ability to flip into the third dimension.
Merlumina was a member of the Tribe of Ancients. 1,500 years before the setting of Super Paper Mario, she was told to protect the Pure Heart in Yold Ruins and await the hero of legend. 1,500 years later, her ghost still waited for the hero to arrive. She is the only member of the sages to be met by Mario and his friends in-game. She is credited with writing the Light Prognosticus by Merlon, although Merloo was also said to be the author. She is distantly related to Old Man Watchitt, with whom she telepathically communicated while impatiently waiting for Mario.
Merlumina's sister brought the purple Pure Heart to Sammer's Kingdom and fell in love with the king. They had 100 children together, providing the origin of the Duel of 100, and making her the ancestor of the King Sammer encountered in the game.
The inventor of the Pixls was a human member of the Tribe of Ancients, as was his daughter by extension, who died and had her spirit transformed into the Pixl Queen, who is implied to have become Shadoo, the creature of shadows and illusions that is encountered at the bottom of the Flopside Pit of 100 Trials. It is also implied that the other Pixls were also created from the souls of Game Overed people, possibly making the eleven Pixls that Mario encounters Ancients. The Ancient magician who created those Pixls also had a son whom he believed had perished along with his wife. However, the son survived, and may be the ancestor of Dimentio.