As with today’s major rollups, Eclipse Mainnet will settle to Ethereum.
Eclipse Mainnet's validating bridge on Ethereum will be directly enshrined into Eclipse. Eclipse nodes will look to this bridge to determine the "canonical chain". The bridge enforces the correct ordering for Eclipse. Eclipse nodes must also run Ethereum full nodes.
This allows our users to gain certain security properties from Ethereum. The bridge will validate all Eclipse transactions, preventing submission of invalid states. Additionally, it will enforce eventual liveness and censorship resistance under certain failure cases. Even if the sequencer were to go down or start censoring at the L2, users would be able to force inclusion of their transactions via the bridge.
Because of these security properties, validiums and optimiums are often referred to as "Ethereum L2s." L2BEAT defines an L2 as "a chain that fully or partially derives its security from layer one Ethereum so that users do not have to rely on the honesty of L2 validators for the security of their funds."
Ethereum settlement recognizes the importance that Ethereum-native assets will likely play in Eclipse Mainnet's DeFi and NFT economies. ETH is the best decentralized money that most users clearly prefer, so we will also use ETH as our gas token. Longer term, fee abstraction will enable users to pay in any token of their choosing (e.g., USDC). There are no plans for Eclipse Mainnet to have its own token at this time.