Currency
The currency used across most of Empyria is known as 
stars. Most iconically, they take the form of iridescent black coins with an eight-pointed star on the obverse side, from which they get their name.
Origin
During the First Age, the Telos civilization minted coins out of stellium, a black metal that changes colour in the presence of mana. Different colours are associated with different types of mana, and higher concentrations cause more saturated colours. In present day, the abundance of mana in the atmosphere means stellium never displays its natural colour anymore, and instead resembles an iridescent oilslick whose colours slowly shift along with the background radiation.
Though the Telos civilization was destroyed during the Cataclysm, much of their currency survived in various caches. These coins were distinctive in appearance, difficult to destroy, and limited in amount - what's more, their colour-changing properties allowed them to function as primitive dungeon detectors. Therefore, the survivors continued to trade them as a convenient currency. Although there are different types of stellium coins, presumably worth different denominations during the First Age, they are all similar enough in weight that they are considered interchangeable in present day.
By the time coining presses were re-invented, stellium's status as a monetary standard was already widely accepted. A few historical governments issued their own coins by melting down and re-minting existing stars, but most continued to use them as they were. Today, such nonstandard coins are unusual historical curiosities, and some consider it lucky to receive one as change.
Banknotes
As time went on, more coin caches were found and put into circulation, resulting in currency inflation. Eventually, it became difficult and cumbersome to transport the stars needed for large transactions. To solve this problem, various governments began issuing paper currency that could be exchanged for fixed numbers of stars at the municipal bank. These eventually merged and evolved into two large systems of representative money, controlled by the Orlisian and Wywish governments.
Although easy to use for daily transactions, banknotes can only be exchanged for stars at specific reserve banks, which can be inconvenient for those who need stellium on short notice or have complicated relationships with the law. They are commonly used by civilians, while many adventurers and traders only deal in coins.
Wywick
Paper money was first developed in Wywick. They evolved from offering slips - small printed cards that would be offered to the spirits in lieu of proper gifts in years of poor harvests. During stellium shortages in frontier towns, monetary values were written onto them and used as a temporary medium of exchange. Eventually, they were redesigned into a widespread currency.
Traditionally, Wywish banknotes depict the current reigning king on the obverse, but the latest King Sylvan chose to use an abstract family crest design instead. The reverse depicts common offerings - flowers, crops, precious gems, and so forth.
Orlis
Since Orlis is a relatively young empire, many of its states were already developing their own paper money by the time they were conquered. As a show of power, the first emperor created a new series of paper money to be used across the empire and outlawed all others. This proved difficult to enforce, though, and some cities managed to dodge this ban by rebranding their money as simple receipts or promissory notes. Thus, there are a few places in Orlis that use money which is completely worthless anywhere else.
Official Orlisian banknotes feature images of historical figures on the obverse and abstract glyph patterns on the reverse. As a security feature, they contain a strip of a stellium alloy that turns bright magenta when exposed to a test spell, allowing most people to easily test a bill's legitimacy without any special equipment.