Pre-Game Report: The Mapping of the Briars

My wife, Jennifer, suggested I do a pre-game show, uh, report before the huge marathon this weekend so I can compare what I think will happen versus what does happen.

The Coming Adventure:  The thieves and such of the campaign, accompanied by the barbarian (custom class) Bridget (arguable the toughest fighter PC) will hexcrawl the entirety of the Briars (map here).

Campaign Background: In 38 years of running the campaign and 36 years of running people through Skull Mountain no one has even considered such a massive undertaking. Three of the legendary monsters of the campaign (Ol' Knobby, Ol' One Fang, and the Red Maiden) live in the Briars. the place is home to lions, giant spiders, ogres, kobolds, etc. The terrain is unforgiving, the weather extreme, and the hunting sparse. NPCs who have heard of this all think two things - 1) if they succeed the map will be incredibly valuable (the king has already agreed to pay no less than 5,000 g.p. for it), and; 2) they're going to all die.

Preparations: The party is staging a massive pack train to Skull Mountain to stash 6 months of provisions there and to leave a guard force of hirelings, henchmen, low-level PCs, and a master cartographer. The base camp will use the various spy ports and the magical oculars to track the party and do a 'master map' overview of their location. The main party, accompanies my a journeyman cartographer, will map the ground.
The party and the base camp each have an elven helm; these allow communication with line of sight and will permit the party and the base camp to check in. The party has Boot of Levitation to ensure line of sight and to provide markers for the cartographers.
The party has a Murlynd's Spoon, an Everfull Flask, and a 5th level cleric to provide provisions for the mapping team, allowing them to travel very light (each member will have two days provisions for emergencies).
The field team also has a Broom of Flying for emergencies and have contracted with another PC so that every Fiveday his messenger genie will meet the field team and take a copy of their map and notes to a secure location in Oldbridge.

That's right - the party is making weekly backups of their data.

Their Plans: The party is going to start in the High Briars just where the badlands begin and start making sweeps through the area to the West of the old road in a roughly circular search patterns covering about 6 square miles each (in other words, they'll sweep a super hex of 7 hexes). In the High Briars with the very rough terrain and the thick brambles, etc. these 'zones' will take about a week to search each.

My Players Should Stop Here

My Prep: I have pre-rolled the weather for the first month of the adventure with a couple interesting things: good weather for a while with a record cold snap, then heavy rains followed by flash floods. Then more good weather with a record heat wave followed by 4 days of constant rain, some thunderstorms, and then - a freakin' tornado.

Existing Threats: If they stick to their planned pattern they will be in a system of arroyos when the flash floods hit and will be deep in the Briars for the tornado. More critically, the few days before the storms and tornado if they keep to their plan they're going to enter the home range of Ol' One Fang.
Ol' One Fang is the last survivor of a tribe of hill giants that in past ages served the Lord of Skull Mountain. He is a maximum hit point hill giant/max level shaman who has a torc of protection +3 worn as a ring and is armed with Manbreaker. Ol' One Fang is very bright (Int 11) for a hill giant and knows the area intimately. The Briars within a few miles of his home is scattered with fighting positions (essentially hilltop foxholes that give him 50% cover and are filled with boulders and have a prepared 'avalanche' of logs and boulders in front of each one he can trigger with a shove). He is a spell caster and if he has any chance to ambush he will have Poison ready.
I have two past TPKs with Ol' One Fang.

What I Anticipate: The party will have the first week go smoothly with an encounter or two. They bad weather will slow them the second week and if they ignore the weather flash flood could hurt or kill PCS. Late in the third week they will almost certainly encounter Ol' One Fang. If they stand and fight characters will die. If they double-down after 1-2 PCs go down, TPK. If they flee or somehow prevail, they face a tornado that could well cause them to flee into unmapped areas.
The bad weather will challenge them especially because it could cut off their ability to communicate with Skull Mountain and prevent them from flying. If things get bad they could use their schedule meeting with a genie to request assistance.

I will update as we play!