The “An Eye for an Eye” scenario.

I'm just curious how, in a month and a half, you can assemble an army from a single Castle capable of defeating a garrison of 140 Lava Dragons, 280 Thanatos, 780 Priests, 780 Berserkers, and over 1000 Riders, and over 1000 Archers and over 1000 Guardians, especially considering that after the first month, you are immediately attacked: first by a hero with 14 Lava Dragons, 28 Thanatos, 30 Priests, and some other minor units (I don't remember the exact numbers), and then, as soon as you defeat him, the main hero attacks with an army twice as strong as the first one (and he is level 26 himself). Not to mention all sorts of non-story-related encounters that constantly pop up.

You can't bypass the garrison using Astral Gates – they are excluded from the storyline.