Here's how it played out.
First, we retreated, heading downriver from where we had been, where we had been attacked.
Then we implemented a series of plans.
Plan A: Try again with flying up to find the limits of the AMF. The answer was, at 1500 feet it began to slope in, reflecting that it was a dome. No going over.
Plan B: Summon an Earth Elemental (Large) to tunnel under the fungus field, using the mass of the earth to block "Line of Effect" from the AMF. The Elemental vanished as soon as it got under the fungus field. AMF penetrated the ground. (The DM had privately warned me about this, but in character I didn't know it, and in good faith had to expend the spells/resources to find out.)
Plan C: Cast Awaken Sand to create an animated construct that was friendly to me. (Spell is from Sandstorm, and is part of the Sandshaper PRC spell list). Since that was a full day casting, the other casters in the party created the "stone hamster ball" that Danny suggested, a huge pipe we could ride in while the Huge construct rolled it across the field.. Before we sealed ourselves in we cast an Augry, to determine if this was a good idea. Signs and portents said it was a bad idea, so we stopped there.
Plan D: Cast Shadow Walk and cross over extra-dimensionally. Note that, in our game, that's a walk by the river Styx, not to be undertaken lightly. Again with the Augry, again, the powers above said "Bad idea".
Plan E: Walk away.
The fact that we reached Plan E is telling. We walked away.
Now, what we didn't know (aside from, like, everything):
1) This group, essentially epic in level, had no background we could learn about because they had just dropped in from another dimension. (Even though Knowledge - Planes had brought us nothing.)
2) Merchants had been dealing with them for about seven years. (Yeah, #1 and #2 disagree, roll with it.)
3) If we had bothered to go back and talk to the nice gate guards who had attacked us, unprovoked, several times as we sat in camp, and had killed several of our friends, who were now a day's walk from where we ended up camping after the retreat, we would have found that there was a supervisor on duty who would have been more reasonable and they might have let us walk through unmolested. Along a path lined with that fungus that infects you with an incurable infestation if you even get near it.
4) The fungus was actually a symbiotic relationship between a fungus and an animal. And all we had to do was take a sample of the stuff that kills you if you get near it, put it under the microscope that we didn't have because they don't exist in our world, and then make our Knowledge - Biology roll. That wouldn't have helped us in any way, naturally, but we would have had a little information.
I don't understand how we missed any of that. I must be slipping.
Anyway, because our game runs a "Round Robin" style, a different DM runs the next adventure. I'm covering the interim, since nobody had anything ready. They're sailing to Norway to escort the body of their friend, the Cleric of Baldur, home for a viking burial at sea.
So we survived.
There's a line I've used many times: If you can't lose, winning doesn't mean anything.
The corollary is also true: If you can't win, losing doesn't mean anything.
