The Gallery: the Permanent Collection. The Gallery, #1

Welcome to the Gallery, where powerful beings enjoy peace, quiet, and the company of each other, where they are free to love as they choose, be it one, many, or anything in between. The Permanent Collection comprises those paintings which never leave the Gallery. The beings within these paintings have bargained with the Curator to stay on forever in return for gifting him their powers, resources, or knowledge.
They help the Curator in running the Gallery, and provide sustenance for the Curator. Today's featured pieces include: The Assistant, about a lonely, misunderstood young man and the unusual new job he is offered by the mysterious curator; The Tycoon is about a rough and powerful man who went missing several years ago, and has every intention of remaining so; Three Kings once walked away from their kingdoms, and now spend their days with each other; The Bastard Son is about a man who once fled betrayal and heartache, and now uses his deadly skills and famous sword to defend the Gallery.
And in The Demon Slayer, an angel arrives to find the gallery under attack, and soon one demon is slain while another falls...