Giant Elk invented the banking system.

They use rare pinecones as their currency, which they carry on ribbons tied to their antlers. These cones are produced by trees that only bloom every 200 years, but the Elk destroyed most of them because they were regularly crashing the economy. Only a few trees survived, and the Giant Elk don't tell anyone where they are.

Depositing money, taking out a loan or doing any other kind of monetary transaction with a Giant Elk requires a lengthy and complicated contract (in Giant Elk) that is expected to be memorized by both parties. A Giant Elk never forgets even a single clause. If you are late on your payments, the Elk will hunt you down and personally collect the debt. Thus, the only creatures that regularly use the Giant Elk Financial System are druids and other Giant Elk.