The setback was quite significant, and everything was slow. The tank refused to gain Knowledge, so he was stuck in a "run, fight, run back to replenish mana" loop. Meanwhile, his equally struggling companions dealt with easier guards. And then, around the middle of the second week, while I was slowly building up my territory, Kreg suddenly attacked with clearly superior forces. I had to quickly deal with the nearest treasure, and even Nagash, not Tant, barely managed to repel the cavalry attack in the last city.
And that was only thanks to the fact that in the last couple of days before the finale, 1) I found a vague valuable chest, 2) I reached level 10 and gained advanced wisdom, which is why I dared to take the chest, and it contained fire, 3) thanks to level 10, I managed to visit the library and get at least some stats for the finale.
Kreg backed off, losing a significant part of his army, killing "everything except" – without damaging the main stack – the skeletons. He either couldn't or didn't want to continue the game.
I couldn't play at the time that we were supposed to, so it's fair for him to take the game as a technical win.
As for how the game was, he had a slight advantage, but it was anyone's game at that point.