After Antonio sees Andrew in Rosie's house, he begs God to forgive him, but he refuses to do so, as he does not forgive such things. Antonio then asks God to forgive Narciso, but he says that if he wants him to forgive Narciso, he will have to ask for Tenorio's forgiveness as well. This shows that deep down, Antonio knows that both Tenorio and Narciso have committed many sins, and that they were both sinful men, and that one was not more deserving of forgiveness than the other.
After a caravan of angry people kill Antonio's family by burning down their castle on a hill, they burn Ultima and cooked the carp from the river in her ashes to eat it. These are some of the things that Antonio loves, which is why he sees them getting taken away by evil. Without all these things in Antonio's life, he would be powerless.
At the end of the dream, the golden carp swims into the starry night and renews all the life that just perished in the chaos. This shows that Antonio's dream was what he thinks would happen if the golden carp decided it was time to clean the world of sin and start everything anew. All things, good and evil, would be renewed into a new life, most likely being born again, as carp who live in the river.