|Fragonard, "The Swing" - from Wikimedia Commons
Muses are so called because they inspire others to greatness. Their loveliness is effortless, like a kind of gravity. They are charmed souls, born for a softer world, and they break through this one like a ray of golden sunlight. To a Muse the world is like so many drifting clouds, which crowd and clash around them in the most terrible storms.
The Muse is essentially an effort to put a magical-realist Monsterhearts character in a D&D game. Their most important resource is relationships. It leverages the GLOG system's Conviction rules to create a mechanical basis for characters' obsession with the Muse. Because the Muse can also give new Convictions to other party members, it can even generate intra-party conflict as incentivizes other PCs vying for their affection and going along with their stupid plans.
My other major goal with the Muse was to make a character who plays to the metafiction. By that I mean that Muses are inherently special, captivating, and powerful, but they don't know that. To them, things just seems to happen. Someone playing a Muse can fully exploit the character's abilities, without anyone in the world suspecting treachery, because technically the Muse isn't doing these things.
In short, the Muse is the Dame in every pulp story, or Chris Hemsworth in the Ghostbusters reboot.
(Play this to set the mood.)
For every Muse template you have, gain 1 Obsessed character and 1 Charisma (Max 18)
1: Obsession, Rejection, Passions
2: Charmed Life
3: Beck and Call, Stalker
4: Redemption, Fury
Obsession: For each Muse template you have, you may have 1 character Obsessed with you. Obsessed characters are in love, pining hopelessly for your recognition. This does not necessarily change their overall motives; however, it does change their attitude towards you in particular. For instance, a rival will still try to burn down the inn where you and your party sleep, but they will try to abduct you first so you aren't caught in the blaze.
Obsessed characters effectively have a Conviction to protect and treasure you (even NPCs, who ordinarily wouldn't have Convictions).
You can attempt to Obsess a character at will, the act needing nothing more than a wink, a smile, or perhaps just the light hitting your perfect skin just so. Targets must be capable of something at least akin to love (so a dog may be targeted, but a zombie may not). The target may Save to resist this effect. However, you can only have as many Obsessed characters as you have Muse templates, and the only way to end an obsession is for the character to die, or for you to Reject them (see below).
Rejection: Ending an Obsession is not quite so easy as beginning one. It requires an act of vileness, performed upon (or at least for) an Obsessed party - something that utterly ruins you in their esteem, and poisons their heart with regret. Their Conviction to protect you becomes a Conviction to destroy you - and indeed, they may go to great lengths to do it. You may not replace this Obsession with a new one until you've had a full night's rest to process the ugly breakup.
Passions: Passions are intensified by the very presence of a Muse. Whenever you are around, replace whatever reaction roll system you use with the following d20 scale:
If your regular Reaction system does not use a d20, double all modifiers from Charisma to these rolls.
Charmed Life: Even the fortunes love you. Whenever you roll a d20, roll a second one, making sure it is easily distinguishable from the first. Call this your Happenstance die. Whenever it shows the same number as the d20, something strange happens. This occurrence does not change whether you succeed, but brings some strange magical occurence into the mix.
For instance, say you are trying to seduce someone and both your Reaction roll and Happenstance die show the same number. After applying Charisma, your result is Neutral. The GM decides your partner is indeed quite taken with you, but has somehow begun to sweat oil paint, and needs to go shower in turpentine.
You may also choose to roll the Happenstance die to invoke some beneficial effect on actions that do not involve a roll: on an 18-20, you and the GM work out some beneficial effect. On a 10 or less the GM describes some decidedly unbeneficial occurence - you must choose either to accept it, or stop using the Happenstance die for the rest of the session.
Two more notes: First, the player always gets to know what happened, even if it's "off screen". So, if a Happenstance on a Stealth roll means the party's hushed whispers reach a villain's ears 100 miles away, the player knows that. (The characters don't, unless they have reason to.)
Second: The Muse does not know they are a Muse, nor that they cause all these odd occurrences. They may have some notion that strange luck follows them, but any promises or plans made on those grounds are sure to go awry. I mean, 100% sure. A Muse diegetically banking on Happenstance gives the GM license to fudge against them.
Beck and Call: Once per Obsessor per day, the Muse may attempt to compel them to carry out a single spoken instruction. The target is allowed a Save to resist this effect, and have Advantage on the roll if the request puts them in mortal danger.
Stalker: Once per adventure, at the player's will (but certainly not the Muse's), an ex-lover, former fling, or spurned admirer will appear to woo the Muse. This NPC acts as a 1HD follower with maximum Loyalty, and arrives minimally if poorly equipped for whatever task is at hand. They are clingy, annoying, and utterly devoted, but will leave in frustration at the end of what they judge to be the current adventure (unless the Muse returns their love, in which case they will run off to slay a dragon in your name or something and surely perish).
Redemption: The Muse can peacefully end an Obsession with several hours' tearful conversation. At the end of this, the Muse makes a Charisma check. If they succeed, they may attempt to Obsess the target again in future. If they fail, the target is utterly immune to the Muse's charms and special abilities.
Fury: The Muse may opt to deal 4d6 damage to an Obsessor they break up with. If reduced to 0 hp they are despondent, and Save or die from their grief. If they survive, they are immune to the Muse's abilities.