Hey! It’s our first mana…manasa…manasap…manasaput…*deep breath* psychic reincarnated Hindu mythology-inspired Positive Energy Plane kinda-angel dude!!!
Pathfinder’s manasaputras are inspired by the ten sons Brahma created from his mind—according to Wikipedia, the name in fact means “mind-born son.” In Pathfinder’s default cosmology, they are outsiders associated with reincarnation and the path to self-perfection. Lawful good beings based on the Positive Energy Plane, manasaputras are benevolent and compassionate but remote and monastic—their touch upon the multiverse is light, and they are more interested in giving mortals tools to solve their own problems rather than wading in to render judgment or do battle.
That is a very quick gloss for a very complicated group of outsiders. Spend some time with the Bestiary 5 entry to learn more—in fact, you’re probably going to want to read it twice. Suffice it to say that the Positive and Negative Energy Planes have always been the z-axis to the Elemental Planes much simpler x/y grid. Similarly, manasaputras sit above the typical good vs. evil tug-of-war for souls; their goals are more mysterious, more esoteric, and more concerned with cosmic truths than cosmic scoreboards.
Manus tend to have entire races for their portfolios; rishi manus have entire worlds. Maharishi manus are the greatest of these. This means they have accessed deeper truths, attained higher levels of self-perfection, and likely tend to larger portfolios—not just planets, but epochs as well (as is evidenced by their mastery of time-based special abilities.) They say little (usually in riddle form) and act rarely, so when they do it is a momentous event.
Adventurers wish to destroy a succubus-wrought artifact that preserves the youth and beauty of the user for an ever-escalating terrible price. The aging touch of a maharishi manu is required to weaken the object enough so that it may be destroyed.
Worlds with several satellites are often tended by a maharishi manu, a being with the foresight to observe a dozen moons (and their inhabitants) as well as the spiritual journeys of those on the planet below. On the world of Beryl, adventurers discover their maharishi manu has left his post. He has decamped to the moon Heliodor, where he has created a paradise full of creatures and races whose evolution he has personally overseen. Unfortunately, this has not only left Beryl and its other moons untended, but also drawn the attention of the vile sahkils, who have begun building a chittering army on Heliodor’s dark side.
A bythos and a maharishi manu are playing chess. Actually, they are attempting to repair a rent in the fabric of time, but they disagree on the precise means to go about this. The resulting spirited debate (spirited for an aeon and a manasaputra, this is) is perceived by mortals as a game of chess that causes episodes of déjà vu and even timequakes across the world. Adventurers might wish to pause the game, make sure one of the players wins, or even challenge the outsiders themselves, depending on their end goal.
—Pathfinder Bestiary 5 164
Alphabetical tidbit: Did you notice that the manu comes before the maharishi manu in Bestiary 5? Not sure if that was intentional or not.