In order for the sidechains to run they require validators who act as the block producers that include transactions into blocks. The validators who are allowed to do so are stored in a validator list that exists on-chain on the Cardano mainnet.
The initial validators will be a hand-picked subset of existing stake pool operators in the Cardano ecosystem who are well known and trusted. Having successfully run stake pools for a long period of time they are incentivized to maintain their good reputations and track records. This makes them the best candidates to kickstart the protocol.
Once the Milkomeda protocol moves into adding Plutus support, validators will be required to supply up-front collateral. This collateral represents their willingness to do a good job, and can be slashed if they have a bad actor escalation case filed against them.
Through the Milkomeda DAO users will be free to add or remove validators as they deem worthy in addition to changing the required collateral parameter. If the initial set of validators can be improved on or the collateral requirement is deemed to be too low, then proposals can be created to replace them. Over time it is expected for more validators to be added to further decentralize the system and make it less vulnerable to collusion.
In addition to being block producers, validators are also tasked with running the sidechain bridge that enables assets to be transferred and for wrapped smart contracts to be called with. The validator node includes all of these capabilities, streamlining the setup experience for validators.
Validators will get paid out every week from the treasury to a smart contract that locks their payout with a two-week cliff.