A virtual trading card in Gods Unchained, a trading card game built on blockchain technology, just sold for $31,000 in Ethereum cryptocurreny. The total sale was for 210 ETH.

The card in question was Atlas, a uniquely minted card from a set of four, identified as a Mythic-rarity Genesis Titan. There is only one Atlas card and, as of this sale, it has been traded from the person who discovered it, to the person who bought it.

Atlas was traded on the digital asset marketplace OpenSea, which enables the trades of blockchain assets from several blockchain-based games.

Blockchains are a technology that uses cryptographically secured, distributed ledgers and rules checking nodes that provide proof-of-work to secure transactions. Through this protocol, a blockchain can become an immutable history of transactions for a digital asset and cryptographic keys can be used to prove “ownership” of that asset.

Blockchain game asset enthusiasts can trade cards from Gods Unchained, cats from CryptoKitties, weapons and armor from Neon District, and numerous other games. It is a well-trod multi-asset marketplace that trades over 4 million assets from more than 135 distributed apps (or dApps), which are mostly games.

As a result, when the Atlas card was traded, the original owner gave up their cryptographic keys to the card and the new owner generated a new set. With those keys, the new owner can prove that they own Atlas and can also trade it to someone else.

The four Mythic Titans are Atlas, Prometheus, Tethys, and Hyperion. The titan Hyperion was sold earlier this year for $62,000. There are only four Mythic-rarity cards minted every year and they come with abilities that greatly affect gameplay aside from their unique rarity.

With Atlas on the game field, both players have 15 Atlas’ Burden’s cards shuffled into their decks at the start of the game. When drawn, Atlas’ Burden summons a random Legendary creature that costs the same or less than the available player mana.

Games such as Gods Unchained belong to a growing trend in blockchain-based gaming that can provide player-owned assets that have provable rarity and can be actually traded.

See Vox Ex Machina’s review of Gods Unchained for a better understanding of how it operates and why these cards can have the value that they sell and trade for.