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The monetary policy basis of the terra project is to create an elastic money supply which contracts and expands through a decentralized arbitrage mechanism. This is where the need for a complementary token to absorb the UST market volatility and act as a medium for arbitrage arises. That complementary token, as originally envisaged, is Luna. When 1 UST < $1: Users can send 1 $1 UST to TerraStation and receive $1 of Luna in return. The peg is maintained through an arbitrage. mechanism that incentivizes traders and market participants to pull the value of UST towards $1.