The octogons could overlap.
Keeping all of what the first post said in mind,
I definately imagine this kind of game that takes place on land, air and sea as 3d.
In the air and in sea, but especially underwater I want to travel up down left right all over. Thats what a fish does. Immersion, realism, good open feeling.
Another reason for it to be in 3d is that it seems to be easier to build worlds that move and change.
Since the land is charged with magical energy and also alignment energy, the visual life of the land could be able to change based on the energy (octogons) it sits on.
Also, w/in the story different kinds of land would have different magic tendencies.
Energy land tends to have:
Forest land looks green, alive. Another challege for a good graphics artist, but basically it has its own alive look and the energy it tends to have lots of is earth energy or the games equivilent to life magic.
The land changing:
Maybe there is a land like Mordor that is very dark.
Of course this land is filled with dark magic.
Beyond this land its darkenss is spreading. If the darkness was spreading it would have an impact not only on the magic content of the octogons but the visual life of the land.
The once lively forest becomes darker.
The towns become darker.
Buildings look craked. Trees aren't quite as green.
It becomes more of a challenge for the charachter to travel.
He has to be better at playing the game as it goes on, not merely do the enemies level up but the magic in the land gives him less and less boosts and helpers.


Subquests:
A creature so dark when it walks on the land it changes the land to polar darkness. That creature: in the forest.
The 'source'...perhaps the source of healing type magic, is weakening and the player can save the source for the surrounding village. Except this source isn't non-existent in game, it can actually be harnessed by the player.
Incredible magic weapons to find.

Well, I was inspired by the post and some ideas came to my head.
I was thinking some other things too but I may write them later.