Cubus is a glyph that creates blocks of stones. Located in the Monastery at the beginning of the game.
it is recommended that the player avoids it until they have obtained the Ignis glyph as i
t is one of the hardest to obtain glyphs, apart from Pneuma. Even if obtained, Cubus isn't very useful except for creating walls that inflicts minimal damage. The glyph is entirely optional, but not recommended. Cubus is Latin for: "A Mass, Quantity"
however it and Fidelis Medusa are the only glyphs capable of petrifying. It's main goal appears to be generating an endless amount of blocks, preventing you from getting a hidden chest. In other words, you absorb it to move beyond an obstacle ; it wasn't designed to be a useful weapon.