The Companion Cube is a pet-summoning item that can rarely be sold by the Travelling Merchant for 5 .
The Cube will spin and jump around the player frantically and, when it touches lava, it emits noises closely similiar to Lunatic Cultist's death sound. If it is submerged for long enough, there is a small chance for the cube to play the Moon Lord death sound instead. Additionally, the cube will ocasionally emit the flatulence sound emitted by the Whoopie Cushion.
A unique ability of this particular pet is that, when the player is in a completely dark place (i.e not illuminated by torches), the cube will ocassionaly attack the player dealing around 2 damage. When the player dies in said manner, the unique death message: <Player's> was stabbed will be shown.
This is the only pet in the game that deals damage to the player, and, like other pets, can also trigger Teal Pressure Pads.
- The pet resembles a metal block with a heart in the middle. Just like all pets, the Companion Cube will follow the player indefinitely until they die or the buff is cancelled.
- Some sound effects made by the Companion Cube will only play once per minute, regardless of how many times it was submerged in the lava.
- The chance of the Travelling Merchant selling the Companion Cube is 1/150 making it a raletively rare item to attain. It is currently the most expensive item in the game, at the cost of 5 platinum coins.
- The Companion Cube is an object that can be interacted with from Portal 1 and Portal 2 Developed by Valve.
- The strange human-like noise it emits when it touches lava, as well as the tooltip and buff tooltip are all direct references to the same item in the Portal games. A possible explanation for the human noises is from the popular internet theory that humans are stuffed inside of the cube.
- The tooltip "Will never threaten to stab you and, in fact, cannot speak." Is a direct quote from GLaDOS after she gives you the cube in chamber 17.
- Added to the game.