The most challenging maps for you.

Ha! I took a look at the situation and progress of Red in your save #3.
1. You need to find an even earlier save: Olema is already standing on the island with the portals of glory, having captured both!
2. The transition at the end of the day to the neighboring islet, where there are Dungeon gates and a seer's hut - it's not Walk on Water, but specifically Flight, because the shores there are blocked by obstacles from all sides. So again – cheating AI!

I won’t say that there are exactly maps of this type, but here, you can try Undead Apocalypse, which I wrote about earlier in this thread.