mistX is a DEX that enables end users to send transactions through Flashbots bundles. All transactions are gasless. However, instead of paying gas to the miners mistX users pay miners a bribe/tip in ETH. The tip is either included in the trade or comes from the user's wallet.
The exchange utilises Flashbots and as such transactions processed via mistX do not publish user transaction information to a public mempool, but instead bundle transactions together. This hides the information from front-runners and thus prevents transactions from being manipulated, front-run, or sandwiched.