9 Kings: Imp, Library, Massacre, and Combustion Build Guide

To run the Imp, Massacre, Combustion, and Library build in 9 Kings, position the Library in your rear rank directly flanked by Combustion and Massacre, then deploy continuous waves of Imps at the front. This setup turns expendable demon units into a frontline pinning tool, grouping approaching enemies into a stationary kill zone while the Library repeatedly triggers automated burn and execution spells.

Core Engine Components

This strategy relies on four specific cards working in tandem to handle wave clear without stalling card draw:

Card Name	Card Type	Core Function	Board Location
Imp	Demon Unit	Low-cost frontline stall; pins enemies in place	Foremost front rows
Library	Structure	Continuously casts adjacent spells at set intervals	Safe backline center
Combustion	Spell / Effect	Stacks burn damage and triggers on-death explosions	Directly adjacent to Library
Massacre	Spell / Effect	High-damage burst strike that executes weakened foes	Directly adjacent to Library

Imps are not used for individual damage stats. Their value comes from their cheap deployment cost and quick spawn rate. When enemy waves advance, Imps halt opposing units and pull them into dense clusters. Combustion applies scaling burn damage across these packs, while Massacre delivers finishing blows. The Library automates this damage cycle by repeatedly triggering both flanking spell cards without relying on manual card draws.

Board Placement and Adjacency

The Library triggers spells based on direct physical adjacency. Placing empty spaces, unrelated buildings, or isolated units between the Library and its accompanying spells breaks the activation loop.

Backline: Place the Library in the center of your back row, flanked immediately by Combustion on one side and Massacre on the other. This ensures both spells trigger simultaneously on every activation cycle.
Midline: Keep the middle tiles clear as a buffer zone. This prevents enemy cleave attacks, piercing projectiles, and rushing units from clipping the Library.
Frontline: Position your Imp spawners in the forward ranks. Engaging approaching armies well ahead of your backline keeps dying Imps and explosion radii far away from your structures.

Drafting Order Across Run Stages

Do not draft late-game components before securing an active frontline. Building the combo in sequence prevents early tempo losses:

Years 1–3 (Frontline Defense): Prioritize Imps and cheap blockers. Drafting high-cost spells or the Library too early leaves lanes undefended, allowing early skirmishers to reach your monarch.
Early Mid-Game (Wave Clear): Draft Combustion as soon as your frontline holds basic lanes. Combustion immediately assists Imps by converting basic melee collisions into area-of-effect damage.
Mid-Game (Automation Engine): Draft the Library only when you have Combustion or Massacre ready to place beside it. A Library placed without an adjacent offensive spell wastes board space and gold.
Late Mid-Game (Execution Burst): Add Massacre to complete the engine. This adds the burst damage necessary to pierce rising armor pools and escalating enemy health bars.

Handling Boss Kings and Sweeping Attacks

Standard boss Kings feature deep health pools and armor values that blunt flat physical damage. This build bypasses high defenses through percentage-based burn scaling. As the Library repeatedly casts Combustion, burn stacks accumulate rapidly on the boss. Once the target's effective health is whittled down, the Library's automated Massacre casts trigger execution damage to finish the fight.

When confronting bosses with wide cleaves that kill Imps instantly:

Stagger Imp deployments instead of spending resources all at once.
Keep a steady stream of single units walking into the boss's path to interrupt movement and force attack animations.
Focus on buying time rather than keeping Imps alive; stalling the boss long enough for two to three complete Library trigger cycles is sufficient to secure the kill.

Deck Thinning and Upgrade Priorities

Keep your deck as thin as possible to guarantee consistent card flow into frontline replacements:

Deck Trimming: Remove basic starter units and unneeded utility cards at every available rest or shop node. Diluting the deck slows down the rate at which you can redeploy frontline blockers.
First Upgrade Priority: Upgrade the Library's trigger cooldown. Shortening the interval between automated casts increases the application rate of Combustion burns and accelerates Massacre executions.
Second Upgrade Priority: Increase Combustion's effect radius to ensure explosions chain across adjacent lanes.
Third Upgrade Priority: Upgrade Imp deployment speed and spawn counts rather than raw unit health, prioritizing uninterrupted lane stall over individual unit durability.