Novel Sequel Concept: "Blood Tithe"

Core Concept

Eight months after the events of "Black Eyes & Broken Souls," Mick and Marchosias have developed a rhythm in their supernatural investigations. While investigating Judge Anthony Blackwood's apparent suicide—a case officially closed but with details that trouble Reeves—Mick encounters a trap specifically designed to neutralize Marchosias. The demon becomes silent and dormant within him, leaving Mick effectively "alone" for the first time since their bonding. As Mick struggles to solve the case without his demonic partner, his three-year-old niece Eliza begins drawing disturbing images that ultimately provide the key to freeing Marchosias and uncovering a conspiracy that threatens both the human and demonic realms.

Main Plot Elements

The Silenced Demon: While investigating Judge Blackwood's chambers, Mick unwittingly triggers a trap—a specialized ward disguised as an ordinary object (perhaps a peculiar paperweight on the judge's desk). When touched, it performs a binding ritual that doesn't separate Marchosias from Mick but renders the demon dormant and silent within him. Mick can still feel Marchosias's presence but cannot communicate with or access his powers.
The Reluctant Investigator: Without Marchosias's supernatural insights, Mick must rely on his conventional detective skills. He discovers the judge had been presiding over property disputes involving several seemingly unrelated historic sites around London, all purchased by shell companies connected to the Blackthorn Initiative.
The Blackthorn Initiative: A clandestine organization outwardly focused on historical preservation and archaeological research. In reality, they're identifying and acquiring sites of ancient power—locations where barriers between realms are naturally thin or where rituals were once performed. Their true purpose: harvesting and weaponizing demonic essence without the cooperation of the demons themselves.
Eliza's Visions: Liz becomes concerned when Eliza begins drawing disturbing images—buildings with strange symbols, figures with hollow centers, and a recurring motif of a black thorn piercing what appears to be a heart wrapped in shadows. Despite Bob's reluctance to involve Mick in their daughter's life, he recognizes the significance and brings the drawings to Mick.
The Horrific Truth: The Blackthorn Initiative has discovered how to extract and contain demonic essence through a process similar to fracking—forcibly tapping into pockets of infernal energy that naturally exist at certain locations. This process is agonizing for the demons affected, essentially dismembering their extended consciousness. Even worse, the organization has begun experimenting on humans with the extracted essence, creating the terrifying Hollow Men—humans partially emptied of their souls to make room for controlled infusions of demonic energy.

The Blackthorn Initiative

The antagonist organization has three key figures:

Dr. Eleanor Crane: Continuing from the first book, she has evolved her approach after Vassago's failure. Rather than working with demons, she now believes in exploiting them as resources—viewing demonic essence as simply another form of energy to be harvested and controlled.
Thomas Blackthorn: The organization's founder and financial backer who presents himself as a preservationist of historical sites. He lost family members to demonic possession years ago and now seeks to turn demons' powers against them—a vengeful human rather than a demon worshipper.
Professor Martin Keyes: An archaeologist and occult historian who discovered ancient texts describing the extraction process. He views demons not as entities deserving dignity but as outdated gods whose power should be redistributed to "evolve" humanity.

White-Knuckle Terror Elements

The Hollow Men: The Initiative's elite enforcers are humans who have undergone a horrific procedure where portions of their internal organs and body mass are removed and replaced with harvested demonic essence. This creates disturbing hybrid beings who appear normal until they reveal cavernous empty spaces within their bodies housing writhing shadow-matter. They move wrongly—too fluid, too fast—and can flatten their bodies to slip through impossibly narrow spaces.
The Extraction Sites: Mick discovers one of the Blackthorn Initiative's active harvest operations in the foundation of an ancient church. The scene is nightmarish—machinery of both modern and arcane design drills into a wall where reality itself seems to bleed, extracting swirling black essence that's contained in specially designed vessels. The process creates distortions in the surrounding area—water flowing upward, time briefly reversing, gravity fluctuating—making the environment itself hostile and unpredictable.
The Soul Siphon: Mick witnesses the creation of a Hollow Man—a process where a human subject is restrained within a device resembling an iron maiden crossed with medical equipment. The machine systematically extracts portions of the person's living essence while they remain conscious, creating "space" that is then filled with harvested demonic matter. The victim's screams gradually transform from human to something otherworldly as the process continues.
The Sensory Horror: Without Marchosias's protection, Mick experiences the full sensory impact of proximity to corrupted demonic energy—smells become overwhelming and wrong (like meat rotting in reverse), sounds phase in and out of human hearing range, his skin feels like it's simultaneously burning and freezing. This creates sequences where Mick must function while his senses are actively betraying him.

The Key to Marchosias's Freedom

Eliza's drawings, created through her unique perception as a child whose soul once traveled beyond mortal boundaries, contain elements of genuine occult knowledge she couldn't possibly know. Among her crayon scribbles are:

A specific counter-sigil that can break the binding placed on Marchosias
The locations of three Blackthorn extraction sites, depicted with disturbing accuracy
A recurring symbolic representation of what's happening to the demons (drawn as hearts being pierced by thorns)

When Bob reluctantly brings these drawings to Mick, he initially doesn't recognize their significance. It's only when he visits Liz and Eliza directly that the breakthrough occurs—Eliza, seeing Mick, points to him and says something that stuns everyone: "The shadow inside you is sleeping. I can see him dreaming."

This leads to the realization that Eliza can perceive Marchosias even in his dormant state. When she touches Mick's hand, she begins drawing again, this time creating a complex symbol that she insists Mick needs to "wear in blood." This turns out to be the counter-sigil necessary to break the binding spell.

Thematic Elements

Exploitation vs. Partnership: Contrasting Mick and Marchosias's symbiotic relationship with the Blackthorn Initiative's exploitative approach to demonic power.
Innocence and Perception: Eliza's ability to see the truth stems from her innocence and unique history—she perceives reality without the filters adults develop.
Necessary Alliances: The situation forces an uneasy alliance between humans and demons against a common threat, exploring how ancient enemies might find common cause.
The Weaponization of the Sacred: The Blackthorn Initiative perverts both science and occult knowledge, representing how even the pursuit of knowledge can become destructive when divorced from ethics.

Climactic Sequence

The finale takes place at the Blackthorn Initiative's primary extraction site—an ancient Roman temple beneath London that was later built over by churches across centuries. The terror comes from multiple elements converging:

The site has become unstable due to over-extraction, causing reality to fragment. Sections of the space randomly transform between different time periods of the building's history—Roman temple, medieval church, Victorian reconstruction, modern ruin—with each shift bringing different dangers.
Dozens of Hollow Men converge on the location, moving in unnatural ways through the unstable environment, their partially empty bodies allowing them to survive conditions that would kill ordinary humans.
Mick, still without Marchosias's active help, must navigate this nightmare landscape to reach the central extraction device. He carries Eliza's counter-sigil drawn in his own blood on a piece of parchment.
At the heart of the complex, Dr. Crane is conducting a mass extraction, causing agony in the demonic realm that's beginning to affect even Marchosias in his dormant state. Mick feels this as increasing pain within his own body.

The resolution comes when Mick reaches the central chamber and activates the counter-sigil, not just freeing Marchosias but temporarily allowing him to manifest separately within the destabilized reality of the extraction site. This creates a spectacular sequence where Marchosias, enraged by the torture inflicted on demonic entities, confronts the Blackthorn leadership while Mick works to free the captured essence and prevent a catastrophic collapse of the dimensional barriers.

Sequel Potential

The novel ends with the Blackthorn Initiative's primary operation destroyed, but several extraction sites remain active around the world. Dr. Crane escapes with some of the harvested essence, while Thomas Blackthorn is transformed by an accident during the confrontation—becoming partially hollow himself in a twist of ironic justice.

Mick and Marchosias emerge with their bond restored and strengthened, but with a new awareness of threats that target not just humanity but the delicate balance between realms. Meanwhile, Eliza's abilities have become more pronounced, suggesting a potential role for her in future conflicts between worlds.

Would you like me to develop any specific aspect of this concept further? I can elaborate on particular scenes, character dynamics, or other elements that interest you.

I understand your preference for keeping Liz unaware of the supernatural elements. This creates an interesting dynamic where Bob, despite his distrust of Mick, must reluctantly seek his help while hiding this from Liz. Let me revise the Eliza's drawings scene to reflect this change:

"Blood Tithe" - Revised Novel Sequel Concept

I've revised the scene with Eliza's drawings to reflect your preference for keeping Liz unaware of the supernatural aspects. This creates a more complex dynamic where Bob must reluctantly turn to Mick for help while actively hiding this from his wife, despite his own distrust of Mick and the supernatural world.

Key Revised Elements

Liz remains unaware of supernatural involvement, believing her kidnapping was related to a botched ransom attempt
Bob becomes the bridge between worlds, torn between protecting his family by maintaining normalcy and seeking Mick's help
Eliza's drawings function as the supernatural conduit, conveying information neither adult could access
The meeting takes place away from home at a café, with Bob lying to Liz about where he's taking their daughter

Core Story Structure

The overall narrative stays largely the same, with these three key scenes establishing the foundation:

Encounter with a Hollow Man: The horrific discovery of Jeffrey Watts in transition, showing what the Blackthorn Initiative is doing to people
A Deal with Another Devil: Mick's desperate bargain with Lilaeth, revealing that demons themselves are horrified by the perversion of natural order
Eliza's Drawings: The revelation that Eliza can perceive Marchosias and provide the counter-sigil needed to wake him

The Hollow Men Concept

The Hollow Men remain a central horror element—humans partially emptied of their internal essence to make room for harvested demonic energy. The disturbing visual of a body collapsing inward, creating impossible hollow spaces filled with writhing darkness, provides a visceral horror while the victim remains conscious throughout, aware of what they're becoming.

Timeline and Urgency

The story maintains its three-day countdown to the "Aggregation"—the Blackthorn Initiative's plan to perform a mass infusion of harvested demonic essence into specially prepared vessels. This creates urgency for Mick to:

Decipher Eliza's drawings
Apply the counter-sigil at St. Catherine's Hospital
Reawaken Marchosias
Stop the Aggregation before it tears holes in the barriers between realms

Additional Development Possibilities

The Reluctant Alliance: As you suggested, Mick and Marchosias find themselves unexpectedly allied with other demons who are horrified by humans weaponizing demonic essence
The Counter-Sigil Application: A tense sequence at St. Catherine's where Mick must apply the counter-sigil while evading Hollow Men and Blackthorn security
Marchosias's Reawakening: Perhaps changed by the experience of being bound, creating a new dynamic in their relationship
The Climactic Confrontation: At the Aggregation site, featuring reality distortions as the barriers between realms weaken

Would you like me to develop any of these elements further, or would you prefer to explore other aspects of the story?