Just play. That's really it. Every Mystery Box in your inventory came from actually playing the game. Here's exactly how finding one works.
Push Objective Tiers The higher your objective tier climbs in a single run, the better your chances of a box turning up before it ends. From tier 3 to tier 10, each new tier you reach is another chance, and the chance grows the deeper you go. This applies to every box type: Mystery Box, Epic Box, and Legendary Box alike. Caps out at Tier 10.
Hold $WUD Your linked wallet's holding tier improves those chances on top of your objective tier, so the more $WUD you hold, the more often boxes turn up while you play. Going a while without a box helps too.
Finish The Run. Seriously. A box only saves when your run actually ends. Game over counts, quitting doesn't. Bail to the menu with a box in hand and it's gone. The game will warn you, but consider this warning number one. One box max per run, there can never be more than that.
Higher Tiers Are Rarer A Mystery Box can pull anything from a modest Common all the way up to a jaw-dropping Legendary, just heavily weighted toward the low end. An Epic Box guarantees at least Rare. A Legendary Box guarantees at least Epic. See the Odds tab for the exact numbers per box.
Remember To Mint Every skin you pull has a real mint window before it's gone for good. Check the countdown on each one in Your Vault. If you haven't linked a Polkadot wallet to your account yet, you'll need to before you can mint anything, so get that connected early rather than scrambling later.
From tier 3 to tier 10, each new tier you reach gives you a chance at a mystery box, and the chance grows the deeper you go. One box max per run. If you win, a golden crate appears in the rock; pick it up and finish the run properly and it goes to your Vault, and your mailbox tells you about it. Holding $WUD and going a while without a box improve your chances.
Every skin has a star rating from 1-10. Higher star ratings mean a harder cap on how many can ever be minted, and once a tier sells out it's gone for good.