Neogothic by Anthony Jerome Brown

In Neogothic, a Fantasy novella, Rob, a recovering addict turned counselor falls - yet again - into shadow...as New York's underworld surfaces at the nexus of three planes of existence...and a Demon Lord is pitted against an alliance of humans and Belladoran races - fairies, elves, halflings, dwarves and dragons - in possession of a powerful malevolent relic...and they bet their lives the horrendous maw of malice will self-devour.