It's the dramatic point. I'm going to have to collapse the empire if I lose, might as well do so in a fashion that gives itself to a legend. ether Triml becomes a legend, or their emperor dose. determine the winner, then tweak the results in favor of that winner. as long as the results are legendary, I'm happy with the results.
still, I got a better then even chance of victory. internal supporters, surprise, and unless he completely foresaw the surprise attack (or really bad luck), the majority of his army elsewhere, and weeks away from being able to counter my attack.
call it a loss of internal cohesion should I fail. with not leader to step up, old clan-politics try to re-surface and tear everything apart. they develop into a Particularly vicious barbarian tribe that occupies the area?
Oh, and if I fail, the codex gets sealed away as a "Lost Treasure". possibly discovered as a historical artifact of great value sometime int he future.