Azurite is a variety on the inkstone, with an exchange rate of 1 azurite netting 1000 inkstones.
Inkstones and azurites, as they have been created by a Sovereign and thus contain a little bit of its power, can be refined into Sovereign's Might, although with tremendous effort and at a huge cost.
Netherstones - The netherstones of the Netherworld were comparable to the inkstones of the Infernal Realm.
In the Infernal Realm, Demigod Artifacts cost approximately 10 inkstones, God Artifacts 1000 inkstones and Highgod Artifacts around 1 million inkstones.
According to the rules, returning to a material plane will cost each Highgod one trillion inkstones, and each Highgod can bring ten Gods with them.
A Seven Star Fiend of the Infernal Realm generally would possess one trillion inkstones in worth at most.