Krazilec is Long-foretold 'battle at the end of the universe.' It was a term used by the God Emperor to denominate the chaotic period after his death, the Famine Times and The Scattering.
Per the Expanded Universe
Kralizec is the long prophesied and expected final battle at the end of the universe. It is sought out by the Thinking machines in the final two Dune novels, Hunters of Dune and Sandworms of Dune. In the end it is not a battle that occurs but a great change that sees Thinking machines and humanity united through Duncan Idaho. Duncan and the Independent robot Erasmus merge and through the utilization of Duncan's abilities as the final Kwisatz Haderach, a new order is formed where Duncan is now the supreme being in the universe, able to control machines and influence humans significantly.