Apollo

Apollo is Lune's twin brother and family golden boy. Was once human; after he died he became a muse like Lune, though much less predatory. He's able to subsist on emotions and inspiration rather than entire souls like his brother, and is open about it so artists can decide for themselves if its a trade they would be willing to make. 

Apollo considers himself a creative genius and his attention is intense, but fleeting. He wants to experience all the world has to offer, and will quickly grow bored of one thing and move on to the next. Between this and the fact that he is a little under three hundred years old, he's decided he's ready to pass on and see what the next life has in store. But more than just that, he wants to find and make amends to his estranged twin, who surely must also be growing tired and weary of this existence, and pass on together. Because of this, occasionally his host artist gets dragged away from their work to pursue whispers of another artist descending into madness, or of a mysterious fire in the middle of the night, or of a body found with no clear cause of death. He's been chasing down threads like these for centuries, but it's so rare to find one that has that familiar ring to it, and even when he does find and pursue a lead it has always been a dead end, his twin having disappeared without a trace yet again. But perhaps he would find news of an art teacher with a fondness for lunar imagery and particularly draining classes interesting...

minor details that i dont know how to fit into the rest of this:

• like Lune he lacks any physical form of his own, needing a vessel to be able to directly interact with the physical world
• regardless of any form or vessel he takes, his hands will always appear blackened and burnt. Using them for things such as painting and other art seems to cause him pain 
• he has pyrophobia 
• he's the older twin, by five and a half minutes 
• very unlike lune, he dislikes deception and is very open about what he is and what he does! He doesn't want people to be afraid of him 
• his strength grows and fades with the seasons and the time of day. He is at his peak on a sunny summer's day and miserable on a stormy winter's night
• bad at criticism. giving or receiving
• he thinks hes very good at empathizing with and understanding other people 
• he's wrong