Two bears will never get along in the same den, and it doesn’t matter that the den is the size of the Universe. Urza the Planeswalker's fight against Phyrexia continues. Dominaria once again threatens to become a springboard for clarifying their relationship. But what can one person, even one with supernatural abilities, oppose to armies of semi-mechanical creatures? And Urza sets out on the dangerous path once traversed by the Thrans, intending to create a new breed of people - a breed of heroes.