Echo has different assets that allows you to participate in consensus: when selecting producers and verifiers such assets converts by rate to core asset(the more asset you have the greater your chance to become producer/verifier).
Example of such assets is SBTC and SETH.
Here are excerpts from the implementation of the system.
In chain_parameters stored field consensus_assets. In this field stored the set of assets that can take part in consensus.
Field consensus_assets can be changed by committie members by committee_member_update_global_parameters_operation.
In global_property_object stored field consensus_assets_prices. In this field stored the set of prices (exchange rates to core asset) that used for each asset.
Field consensus_assets_prices changes on maintanance. It recalculates according to asset's field core_exchange_rate.
asset_object and asset_options
In asset_object stored field asset_options options. In options stored core_exchange_rate with the price (exchange rates to core asset) that used for that asset.
Field core_exchange_rate changes by asset_update_operation or set on asset creation.
While selecting next producers/verifiers assets from consensus_assets changes to core asset by rates from consensus_assets_prices and such assets have the same rights as core asset after exchange.
So, by this way, users that holds assets from consensus_assets can participate in consensus.