Rain (RAIN) is a completely decentralized prediction markets protocol constructed on Arbitrum that includes cross-chain capabilities. Often described as the 'Uniswap of prediction markets', it provides an open framework allowing anyone to launch and trade custom markets without limitations. The system offers Private Markets for restricted, invite-only community forecasting, alongside Public Markets settled via an integrated AI oracle. To handle disputes, every resolution is supported by a decentralized arbitration mechanism featuring both an AI "judge" and human oracles. Additional features include secondary trading, account abstraction for improved usability, and a deflationary token structure where 2.5% of trading volume is used to buy and burn $RAIN tokens. Token holders manage the protocol's governance through a DAO.