Underkeep is a strategy simulation game for PC in which players take on the role of the final boss defending a labyrinth against waves of adventurers. The core loop centers on constructing and refining a dungeon layout that grows more effective with each successful wave, turning the environment itself into a personalized defensive system.
Gameplay
Players dig corridors, position monsters, and set traps to create challenging paths leading to the boss room. All placements persist between waves, allowing the labyrinth to evolve into a custom design shaped by repeated encounters. With 35 monsters, traps, and special zones available, builders can fold paths back on themselves using walls so that individual traps activate multiple times against incoming groups.
Preparation relies on reading wave previews that reveal the composition of the next group of adventurers. Miners target walls directly, sappers disarm traps, and rogues may bypass certain defenses entirely. Adapting the layout to counter these specific threats forms the central decision-making process. Gold spent on upgrades influences whether the focus leans toward physical defenses or mental effects, exploiting the weaker attributes of each adventurer type such as warriors vulnerable to mental attacks or mages susceptible to physical ones.
Defeat resets the current labyrinth but preserves progress records, enabling subsequent runs to extend further. The first encounter with any adventurer class pauses the action to display a card detailing its strengths and weaknesses, providing immediate guidance for counterplay. Controls support precise placement with left-click selection and dragging, right-click removal, space to launch waves, and dedicated keys for the shop, land expansion, boss room movement, rotation, speed adjustment, and settings.
Game Modes
The game operates through sequential waves in a single persistent building session per run. No separate named modes exist beyond the core wave-based progression, where each cycle builds directly on the previous layout without resetting placed elements.
Core Mechanics and Progression
Resource management revolves around gold earned from defeated adventurers, which funds new purchases in the shop accessed via the S key. Shop interactions allow left-click selection and purchase of cards or right-click inspection without commitment. The system emphasizes iterative improvement, with every wave providing feedback on what worked and what requires adjustment in the next cycle.
Language support includes Korean, English, and Spanish. The developer notes that the experience inverts traditional tower defense by placing the player in the defensive position, with no hero progression on the attacking side and instead a sharpening labyrinth over time.
Is It Worth Playing?
Underkeep suits players who enjoy deliberate strategy games with simulation elements, particularly those drawn to iterative building and adaptation against varied threats. The persistent layout changes and wave preview system reward careful observation and redesign rather than reactive clicking. Its indie casual approach keeps sessions accessible while the simulation depth emerges through repeated runs that gradually extend survival distance. Those seeking a fresh perspective on defense building without complex multiplayer layers will find the focused single-player loop engaging for short to medium play sessions.