I'm at the point in the game right after the trip to Archades, and I'm about to head back to the Feywood, and on to (SPOILER)Giruvegan. However, instead of proceeding, I've decided to go for the Rank VI marks, and 3 of them (so far) are in the Nechrol of the Nabudis and Nabudis Deadlands.

Aside from these marks, there it doesn't seem necessary (at least from a main storyline point of view) to venture into these areas. In fact, when you enter the Deadlands there's the scene with Basch, where he simply says in his own way "we shouldn't venture any farther, the enemies are tough".

Are these areas necessary for the storyline? Or are they purely optional? Either way, I intend on exploring them, I'm just curious.....