So we fake a suicide charge?
Yes, but we don't go far. Look, I've described the plan before. We arm the children and the wounded to appear that we are going all-in and making our last stand. We force some of the creatures to run at our group with a few suggestions, the children scream and run for the chapel, our ranks are broken, the Reds try to rein the people in - you get the picture. We don't get far from the building before all of this happens. We pull back to stop the panicked retreat, and we don't manage to close the gates behind us.
At this point I expect to have all of the minions charge at us, because why the hell not? It's a free meal.
If - somehow - Miosguinn manages to stop the horde, which I don't think he can, BTW, we just close the gates and think about something else.
We will definitely not get lured in attempting the actual suicidal charge.
There is nothing in D about preparing the grenades and they are our only chance at taking down his illusions.
The grenades can only be prepared if we are sieged. That is A, D and E (if it does not take place immediately).
But only if we want to make them. I guess it can be put to a vote.
We can't track him down and kill him, he's an illusionist with a vast magic supply and very familiar with the current terrain with no dependents.
So how would he hide from the pathfinders? Illusions don't work if you are not there to maintain them. And if he tries to hide with magic, Nine should feel him manipulating the energies. One dispel grenade thrown at where this manipulation manifests itself the strongest, and he is done for.
Look, you are not tricking him with C2. His goodwill extends as far as his warning to us. If we didn't heed it, too bad for us. He will not believe that a bunch of do-gooders like Gareth and/or Tyrvard who are war vets will betray the king they fought for, and he will never belive Derryth will be okay with putting them to death. There is no reasonable bluff that would work. So if we ever attempt Miosguinn diplomacy, we will be the ones walking into a trap, not him.