The Eldritch Widow's Whisper

Elara, an abyssal progenitor disguised as a human widow, is forced into a dangerous soul-symbiotic contract with Elias, a righteous detective. Hunted relentlessly by the council of elders, the two face off against an ambitious duke and a lord of a terrifying dimension in London, fighting through bloodshed and tension to stave off an impending higher-dimensional catastrophe.