Callisto's core is based on Ethereum, but its a mainnet project now, offering security audits for smart contracts. The project has a very unique usecase and a good number of holders too. $CLO latest transcactions are from mining operations, though it can also be used to make quick transactions, thanks to its 13.5 average blocktime.
Also you can mine $CLO, or Cold stake (Use of smart contacts to reward users after 27 days) on popular wallets like Coinomi, Magnum, Guarda or Trust wallet (at the time of writing this review) for passive income.
I like their brand and lately, they have begun a push into Decentralized finance, making audits on MakerDAO and other "DeFi" related projects to ensure safety in smart contract transactions. It seems Callisto is actually solving a problem in the crypto space and I commend that.