This also may help your understanding - a quote from a lead dev on the project:
[In reply to John Denver]
Hey John. THORChain is a blockchain in and of itself! A network of anonymous nodes bond RUNE to underwrite assets in pools; and like other blockchains these nodes together form the blockchain via consensus & block production.
THORChain currently "observes" binance chain, meaning nodes all run a binance chain node and make witness transactions about what they have seen. The network reaches consensus about the observations and state is changed.
The team is busy integrating Bitcoin, Polkadot, Cosmos and Ethereum so THORChain should be able to observe multiple chains and enable true cross-chain swaps by end of year.
Thorchain nodes will be observing transactions on each chain they link to to facilitate the cross-chain swaps.
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