Mints can be used to print entry tokens for Tournaments. Each token costs 10 kSAT, and gets returned to the Tournament Organizer after it completes. Organzers can then cash the tokens back in for Bitcoin at the mint. Any tokens that are not used can be lost if players don't use them, and don't return them.
Mints unlock for non-governors at Level 13. Governors can always use Mints.