Bob attacks Sue with two Grizzly Bears, one of which Sue has enchanted with Backfire, which will assign 1 damage to Bob for each 1 damage the enchanted Bears deals to Sue. Sue lets the enchanted Bears through and blocks the other with her Goblin Hero. At the end of damage prevention, the first Bears and the Hero have dealt 2 damage to each other, and the second Bears has dealt 2 damage to Sue. The Backfire triggers, assigning 2 damage to Bob, but first the current step ends, so the Hero and the Bears it's blocking are killed, and Sue loses 2 life, Note that if Bob or Sue wants to regenerate the Hero or the Bears or use triggered abilities such as Soul Net's, they'll do so before the second step begins.