For some reason, this one is a she? Not like it would be a female legendary, but just like how sometimes we say 'he' when we mean 'it' referring to genderless pokemon here you'd say 'she' instead. I can't explain this, it's just a she.
Materiim's name derives from a Latin word for matter (materia and rem as well to an extent) and 1/M, as in E×1/M =C^2.
Materiim, unlike Lucicaz or Navex, is almost completely intact in its Nether Forme. It stands motionless for long periods of time in the clearings of secluded forests, growing moss and rusting until it again feels the need to move. It once remained in the same location for thirty years and it was feared that Materiim had somehow died, though evidence suggests that it has remained in some places for up to a century in the past. A great celebration was held when it finally decided to move again. Small statuettes of it are made and sent to its location to be blessed. While Materiim stays still, these sculptures seem to slowly absorb its energy, growing a moss that never seems to die. If there are statuettes at its feet when it decides to move again, it will drop them off at the nearest settlement and continue on its way. These statuettes are said to provide stability and persistence to their owners and are sometimes given to the family of those who are gravely ill. Materiim, along with Lucicaz and Navex, arrived on Earth many ages ago. Its impact is said to have set plate tectonics in motion.
Pokemon (c) Game Freak, Materiim and Art (c) Me.