The opponent attacked the castle with a million archers, but they don't deal much damage through the walls...
There was a funny fail: when the opponent entered my base, I hid in the snow and was leveling up a separate unit to cast a lightning spell from Solmyr onto Nila. And finally, I leveled him up, ran up with Nila, but I forgot to take Wisdom =)
Luckily, I had enough movement points to get into the castle, and the opponent attacked the next day.