Immutable X is a next-generation protocol for trading Ethereum NFTs which gives users instant trade confirmation, massive scalability, and no gas fees without compromising user custody. Their goal is to make minting and trading Ethereum NFTs even easier than trading traditional digital assets. Immutable X uses a ZK Rollup: Immutable X take thousands of off-chain trades, generate proof that these trades were all valid and then publish that proof on-chain, where it is verified by a smart contract. During this process, the on-chain user assets are held in the smart contract, and can only be released after valid proof including them has been published in a batch.
Immutable X is built by Immutable in partnership with Starkware, the company providing L2 scaling for prominent DeFi applications like dYdX. They don’t have a token yet but a very interesting project to watch out for.