cui et fortuna ipsa praebuit materiam

Orberg Cap XLIII - Tullus and Mettius have agreed to discuss how it will be decided which will rule the other.

Haud displicet res Tullo, quamquam cum indole, tum spe victoriae ferocior erat. Rationem ineunt, cui et fortuna ipsa praebuit materiam: Forte in duobus tum exercitibus erant trigemini fratres.

These things [ideas] were not displeasing to Tullus, even though in his mind and then by the hope of victory he had been the more fierce. They entered into a deliberation, to which fortune itself would provide the means [materiam]…

quamquam cum indole animi, tum spe victoriae ferocior erat – “although he was more aggressive, not only because of his innate character but also because of his expectation of victory”

Rationem ineunt, cui et fortuna ipsa praebuit materiam – "They enter into a plan, for which chance itself also provided the opportunity. . . " This is a little obscure, but I think that’s the idea.

Many thanks.