Mountain Cube

Mountain Cubes stay stationary until the player lines up with them horizontally or vertically, causing them to slide towards the player and attempt to deal contact damage. Mountain Cubes explode when killed, damaging and freezing nearby enemies but not harming the player. If they are still alive when the rest of the room is cleared, they will melt without exploding. Mountain Cubes also leave water wherever they slide.

Trivia

 * In the physical Ammonicon, a Blizzbulon is shown transforming into a Mountain Cube, showing a connection between them.
 * Mountain Cubes are inspired by similar enemies in Fork Parker's Holiday Profit Hike, one of Dodge Roll's previous games.
 * The Ammonomicon entry for the Mountain Cube references them being "known to exist outside of the Gungeon", a reference to Fork Parker's Holiday Profit Hike. The Ammonomicon entry also says that they can be "seen wearing tacky sweaters", which matches the visual appearance of these enemies in Fork Parker's Holiday Profit Hike.

Lead Cube
Lead Cubes behave like Mountain Cubes, but cannot be damaged or killed until the room is completed. However, Lead Cubes can be transmogrified before the room is completed.

In Exit the Gungeon

 * Lead Cubes do not appear in the Enter the Gungeon sequel Exit the Gungeon as enemies, however they do appear as drifting obstacles in the minigame 'Helmet Kicko'.

Flesh Cube
Flesh Cubes behave like Lead Cubes, but leave trails of fire whenever they slide. When they collide with an obstacle, they send bullets in all directions. They cannot be damaged or killed until the room is completed, and they die when the rest of the room is cleared. As with Lead Cubes, they can be transmogrified before the room is cleared.

Trivia

 * The Ammonomicon quote, "a pound of flesh", is possibly a reference to a line from Shakespeare's "The Merchant of Venice". The villain, Shylock, demands a pound of flesh from the main character.