Cave Story Wiki
Monster X
Original Monster X sprite Remastered Monster X sprite
Original Remastered
Location Labyrinth
Health 700 HP
Attack(s) Deploys projectiles and homing missiles
Credits description
Big boss in the labyrinth

Monster X (モンスターX Monsutā X) is the second boss fought in the Labyrinth.


Monster X is encountered in Labyrinth W, to the player's right of the Camp. Players will eventually see the dormant Monster X near the start of an open area populated with enemy Gaudis. Two small hills are seen to the right of Monster X. Upon going a little to the right of the first hill, the boss battle initiates. Shield walls activate on either side of the space to prevent Quote from escaping.


Attack patterns[]

Monster X uses its treads to move along the tunnel, chasing Quote. When it passes Quote (either because the player jumped over the ground treads or it pinned the player against the shield walls) it skids to a halt and switches direction. After shifting directions three times, the boss opens its centrepiece, revealing four collections of green dots in the center. These dots fire a continuous stream of purple projectiles towards Quote, similar to the ones the flying Gaudis attack with. All four of these green spots must be destroyed for the boss to progress to its next stage of attack. The boss keeps its doors open for about five seconds before closing them and moving back and forth again.

When all four of the circles are destroyed, Monster X fires four homing "fish missiles" that are light-green and appear to have an eyespot. These "fish missiles" will circle around and attempt to target Quote.


In order to deplete Monster X's health meter, the player must first destroy the four green circles hidden by the doors. Once the circles are gone, the player is then able to damage Monster X whenever its doors open by hitting the area exposed by them.

A good way to deal with the projectiles is by using the level 3 Blade to shoot at one side of Monster X while running away to safety. This is especially crucial in Hard Mode.

The true form of Monster X

The boss itself is harmful when moving on its treads. If Quote runs into a tread while Monster X is moving, he loses 10 HP. Getting hit by a homing missile causes Quote to lose 5 HP. When Quote runs into one of the shields, he loses 1 HP, and being shot by a spinning purple projectile deals 3.


When Monster X is defeated, a massive explosion occurs, and a cat is seen in the air with its head facing towards the ground. The cat then falls behind the floor as the victory message is displayed. Quote can then proceed and enter the door on the far right, which leads to Labyrinth B and eventually the Boulder Chamber.


  • At the Labyrinth Hospital, the Camp, there's an unused dialogue that talks about Monster X, a mysterious robot that you have chances to attack when its hatch opens.