The monolithic registry is the cornerstone smart contract that operates a mapping of your device keys with their associated account contracts across any Ethereum network.
The Abridged paradigm is to use a public-private key-pair that lives locally on your device or browser instance solely for access purposes, and store the actual funds in your account contract.
Your device key address is used as the salt to generate the unique account contract address and the special accompanying instant deposit contract address.
The registry contract stores the mapping between the device address, account address, and instant deposit address.
This mapping also includes the chainID of each device address so that it knows which network each account contract is signing transactions from. This provides tremendous convenience in using the same account address across all Ethereum testnets and the mainnet without being exposed to any attack vectors associated with having different account addresses across networks.
The registry contract contains all of the deployment logic associated with your account contract. That leaves only the need to verify that the msg.sender is the proper device key to sign transactions. This makes the account contract extremely lean and reduces the base deployment cost down to under 100,000 gas.