With a name that recalls both stern angels and Hindu storm deities, you know maruts mean business. And since their business is the slaying of those who have lived too long, PCs have a better-than-average chance of running into them.
Of course, the question is: What makes a marut take action? Are all the ancient wizards and liches out there just at the back of a very long list, and the maruts just haven’t gotten around to them yet? Or are maruts saved for particularly egregious cases—say, 10 lifetimes lived or the sacrifice of an entire town to power the magic? Or do you have to cross some threshold—perhaps enter or leave the Outer Planes—to tweak the maruts’ alarms? And does killing a marut earn you a pardon, or will another activate to take its place?
For the GM, what’s fun about maruts are the spell-like abilities and the cinematics: plenty of spells to help the marut find its quarry (true seeing, locate creature), make a grand entrance (air walk, dimension door, plane shift), prevent escape (wall of force), and then fists of thunder and lightning and spells that deal a lot of collateral damage (mass inflict light wounds, earthquake). Maruts are your chance to play the avenging angel (or rather, inevitable) to the hilt.
Two displaced nations divided by faith and race have squabbled over the same holy ground for centuries. Now a peace treaty that could end the violence is about to be signed. Neither side fully trusts the other, of course, but both sides trust the saintly half-elven prelate overseeing the accords. Unfortunately, the prelate has cheated death for generations in his pursuit of this very settlement A marut has arrived to slay him, and if it succeeds the treaty will never be signed.
The rise of the samsaran race has caused a dispute over jurisdiction in the Court of Gold and Bone. A splinter group of maruts has decided that the blue-skinned reincarnating people are in violation, and their members begin to execute samsarans one by one. The Court’s remaining axiomite and inevitable officers need mortal agents to subdue and reprogram or kill the faulty maruts.
Fleg is a legendary arcane trickster who once even managed to snatch and depower the phylactery of a lich—but in doing so, tainted her own soul with the lich’s essence. Now a marut with orders to slay the lich has both the undead and her in its sights, considering her a vessel for the bone wizard’s evil. Fleg needs bodyguards to shield her from both the vengeful lich and the implacable inevitable while she pulls off one last score: rather than fight her sentence, she’s going to solve her marut problem by stealing a little divine immortality—after all, goddesses don’t come with an expiration date.
—Pathfinder Bestiary 2 166