Muramasa is a Servant, a superghost with a whole stock of weird conceptual and narratively reactive skills that can influence the role he takes in the stories he is a part of. One of them is an ability called Karmic Eye.
"An ability that is dormant within one's body. It's a variation of Clairvoyance, and enhances both static and kinetic eyesight. It is a type of insight specialized for combat. He lacked the proper foresight of Clairvoyance... or at least that was supposed to be the limitation...but with Muramasa spending his lifetime peering into destiny in the flames of his forge, his eagle-eyed gaze not only enabled him to capture his prey, but also fate itself."
things we can use it for
Got a character who's full fake nice-ing it and is due for some bitchy CR because of their absolutely rancid secret vibes? Or maybe someone seems like an absolute shitheel who has a heart of gold and just can't get anyone to realize? Need a sympathetic ear despite appearances? Here at Peepaw's Sword Emporium, we have a Convenient Narrative Mechanic that can help overcome even the best acting and the worst behavior: the Turbo Karmic Vibe Check.
In short, I'm looking to take a gameplay skill mechanic that is functionally just an anti-invuln skill in F/GO that only gets brought up in one actual story section (and a pile of other scenes that you realize is happening on subsequent rereads), and make it into a fun little CR booster, and maybe just a chance to wax poetic about the nature of fate and humanity or something. All sentient beings have the potential for Buddhahood, after all.
This mechanic is opt-in only! If Muramasa can't get a bead on someone's
vibes karma, he'll just assume it's because his LILITH-built manifestation isn't as sturdy as his original one. He's also NOT A NARC about other people's shit; he minds his own business and won't go around blabbing people's secrets
unless you want me to. Muramasa is a Chaotic Neutral individual, and will permit a lot of truly rancid vibes and behavior (looking at Douman and Rasputin) for the sake of his job, which right now is working for LILITH, but please bear in mind that he does have limits because he still cares about justice just a liiiittle bit at the end of the day.
If you want more information about Muramasa in general, please see his general
permissions post!