Games like King's Downfall
Games like King's Downfall include Factorio, Oxygen Not Included, Prison Architect, Farthest Frontier, and shapez. We matched them by the tags players give King's Downfall on Steam (Strategy, Base Building, Turn-Based Strategy, Auto Battler, and Resource Management): closest matches first, and among equally close ones the better-known games.

Factorio
Shared: Base Building · Strategy · Resource Management

Oxygen Not Included
Shared: Base Building · Resource Management · Strategy

Prison Architect
Shared: Base Building · Strategy · Building

Farthest Frontier
Shared: Strategy · Resource Management · Building

shapez
Shared: Base Building · Strategy · Resource Management

Sid Meier’s Civilization® VI
Shared: Strategy · Turn-Based Strategy · Turn-Based

Manor Lords
Shared: Strategy · Base Building · Resource Management

Mindustry
Shared: Base Building · Strategy · Resource Management

Frostpunk
Shared: Strategy · Resource Management · Base Building

Kingdoms and Castles
Shared: Strategy · Resource Management · Base Building

Captain of Industry
Shared: Base Building · Strategy · Resource Management

Against the Storm
Shared: Strategy · Base Building · Resource Management

Legion TD 2 - Multiplayer Tower Defense
Shared: Strategy · Auto Battler · Base Building

Dota Underlords
Shared: Strategy · Auto Battler · Casual

Game Dev Tycoon
Shared: Strategy · Casual · Indie

ShellShock Live
Shared: Strategy · 2D · Casual

SimAirport
Shared: Base Building · Casual · Strategy

Dyson Sphere Program
Shared: Base Building · Resource Management · Strategy

XCOM: Enemy Unknown
Shared: Strategy · Turn-Based Strategy · Base Building

Foundation
Shared: Strategy · Resource Management · Base Building

Cookie Clicker
Shared: Casual · Indie · Resource Management

Cities: Skylines
Shared: Strategy · Building · Resource Management

Age of Empires II (Retired)
Shared: Strategy · Base Building · Resource Management

Workers & Resources: Soviet Republic
Shared: Strategy · Base Building · Resource Management