Black Monoliths are a type of rock famous for their smoothness. It is quarried out of the ground as a single massive stone. These raw black monolith has to be cut into slabs before it can be used in construction. Due to it hardness this can only be achieved with obsidian or diamond saws. This makes black monolith slabs very expensive, making it a status symbol to build one's house out of it. Slabs made out of black monolith are known for their sturdiness, making them excellent for the construction of defensive walls or to enhanced buildings.
Black Monolith is a non-reflective material. When it is found underground a monolith is usually an extremely flat and rectangular with a smooth surface. It is known for its hardness, scoring a 10 on Mohs' scale of hardness. Black Monolith is often found near ancient volcanoes and other sites related to the age of divinity. When found underground they often make perfect rectangular shapes of 4 meters wide and 13 meters high. It is rare to find more than one black monolith in a 20 kilometre radius from another, thou clusters do exist.
The people of Sahul associate Black Monolith with divinity because of the places where it is commonly found. Because of this most of the religious statues inside of wealthy communities are crafting from the black stone, however this has also caused the dragonborn to see the usage of these sacred stones to be heresy.
Black Monolith by some jokingly called the "Evil twin" of marble for its similar looks, usages, and exuberant price. While elves and especially dwarves prefer to use marble, humans and orcs rather use black monolith and form the core of its consumer base. The gnomes are all to happy to supply the precious stones, assaulting Dragon-kin temples and quarrying sacred lands to get their hands on it.