[Endoperez]

It's because computers can't roll actual dice. There are various ways to try and simulate true randomness, but even the best simulations aren't perfect. There might also be compromises needed to ensure the results are same in all platforms Dominions works in. I think there was a bug with one spell (Magic Duel?) that used different random number generators in windows and linux, and thus got different results in different OS's, and thus battles played way differently (lowly Shaman one-shots a Wyrm pretender OR the pretender kills the whole enemy army).