Orad is a rock containing the essence of magic. It was first discovered many centuries ago, and sparked the explosive growth of the city. It has now become very rare after the rush that followed when it was discovered. To dig more up you need to dig very deep, which requires a lot of capital since the working conditions at the bottom of the tunnels are terrible, and you need the infrastructure to get it back to the surface, extract the Orad, and guard the whole operation.
Smashing an Orad crystal will create a portal to a different dimension (most of the time). To what dimension and where in that dimension is random (although there are efforts to predict/control where the portals open up to). These portals are another reason why the city is so densely populated: beings from all dimensions travel through here, it serves its purpose as a large inter-dimensional metropolis and traveling hub. Small crystals may create tiny portals that stay open for half a second, while the largest will create portals several meters high that don’t seem to close at all. There are a number of sizable portals still open from the time Orad was first discovered.
There are several efforts underway that are trying to crack the mystery of Orad. How does it work? Can we predict where the portal leads to? Can we control where the portal leads to?
Orad is also an extremely powerful drug, causing strong hallucinations to the user, where even a sand-grain sized crystal can knock anyone into a hallucinogenic spell lasting a week. It is very common as a relaxing, mild drug in the form of cigarettes, where it is mixed with other chemicals to mitigate the effect. Usually these cigarettes contain only microscopic amounts of Orad, making the effect very mild and suitable for frequent use. Most people in the city are addicted to the cigarette form.