Tar

A dark substance like the plane itself. Its many uses speak more of the inhabitants' resourcefulness than of itself.

— An outsider's scholarly treatise on the shadow plane

Tar is a black substance usually found in liquid form. When liquid, it is highly viscous and sticky, although its consistency may change depending on the ambient temperature.

Abundance

Natural occurrence

Tar pits are quite common in the plane of shadow; certainly, much more than in other planes.

Magical creation

Through shadow and transmutation spells, many water surfaces of the plane have been converted to tar.

Trade

Many cities struggle to get enough tar to supply their demand. Those cities import tar from other places across the realm. Those cities which have secured themselves wizards capable enough to transmute some of their water sources into tar do not have to worry about that.
Outside of intraplanar trades within the plane of shadows, there is a great deal of interplanar trade. The Godless Realm imports quite a bit of tar, usually via fetchling merchants. The plane of fire also has a booming need for tar, which many in the shadow plane are happy to oblige to. The material plane is a small market in comparison with the previous two, but certain areas do acquire significant amounts of tar.

Other names

Bitumen
Shadow gold
Black soup

Uses

Waterproofing
Building (mortar and cement)
Adhesive
Flavouring (food and drink)
Medicinal
Ignition
Alchemy
Dye

By-products

Black skellies, tar mummies, black puddings, tar spawn...
Whenever one of them explorers go into the tar pits looking for treasure they awaken one monstrosity after another one. And we are the ones who bear the price!

— Zark'ta, a tar mining wayang