The idea is to deploy a Tendermint light client as an embedded contract on NoM to provide a bridge between NoM and Cosmos based chains (the extension-chain is a Cosmos chain fork).
“Light clients (and full nodes) operating in the Proof Of Stake context need a trusted block height from a trusted source that is no older than 1 unbonding window plus a configurable evidence submission synchrony bound. This is called weak subjectivity.”
“IBC uses light clients in order to provide trust-minimized interoperability between sovereign blockchains. Light clients operate under a strict set of rules which provide security guarantees for state updates and facilitate the ability to verify the state of a remote blockchain using merkle proofs.”