I immediately took all of Isabella's troops, and when the sea raiders appeared, I sent Isabella herself to the monastery. My blitzkrieg didn't work out. Godric crushed me. Subordination and berserk didn't help. So I went on a journey around the islands. There I significantly increased the number of archers and acquired artifacts. And even the inquisitors joined. Now I just need to visit the last island - where the Sphinx is. And at the same time, troops are being produced in two castles and two dwellings for the battle with Godric.
Markel only received the Portal to the city from Isabella. There are no Astral Gates. So, jumping across the rocks won't work. I'll have to fly on wings.
I played it similarly, except for the trip to the Sphinx - it's an absolutely useless activity.