The lack of mana in the battle was the deciding factor; perhaps it would have been better to take the center Castle first and then drive Kreg out of the center through raids.
After the battle, I scouted the center — all exits lead through the opponent, I didn't make it to the Dragon Utopia in time, and there is simply nowhere to get money for buying archangels on 131.
Seeing that Kreg took +3 to all and a box of 10 cavalry, I realized there was no point in continuing.
Thanks for the game!