Similar to the Rise of Tiamat – Dragon assets [Major spoilers] question, there appears to be a big lack of guidance regarding the final battle
In Episode 1 p23, it says:
If a faction’s final tally equals or exceeds the “Score Needed For Support,” the characters have won that faction’s full support in the final battle. If the tally is below the score required, that faction sends only minimal support that won’t help in the final confrontation. The benefits of each faction’s support are determined in the final episode, “Tiamat’s Return.”
However, without repeating what is said in Episode 9 pp86-87 very little information is given to deliver on the promise given above.
Speaking generically (those who know the module will be able to fill in the specifics), the PCs have the opportunity to acquire "assets" during the adventure that can neutralize the "assets" of their enemies. If they acquire all of the assets then they should have a relatively easy run through to the climactic battle we have all been waiting for. A few encounters with skirmishes between the "assets" of both sides where the PCs can weigh in to tip the balance without draining too many resources and the party gets the idea that they are a small (but vital) part of greater things and away we go.
However, it is more than likely that they will not have been able to acquire all of the "assets" leaving unopposed enemy "assets". For example:
If the characters fail to get the metallic dragons on side (a distinct possibility), then the chromatic dragons are unopposed. Even assuming that there are only "dozens" of these and allowing that they will be of all different age categories, then either: they will make mincemeat of the PCs or destroy one or more of the allied factions.
Obviously, if they totally blow the acquisition of "assets" their chance of reaching the big final scene would be practically zero.
I am conscious that the question I am about to pose steers dangerously close to seeking opinions so I will be very specific.
What strategies can be employed to:
- Make the acquisition of "assets" meaningful, and
- Make the allocation of those assets significant, while
- Allowing the party a reasonable chance of reaching the big boss battle?
To get you started, I am thinking (embryonicly):
Devising some sort of rating system of asset vs asset (taking into account their differential strengths and weaknesses) and deriving a timeline of the battle so that there are more or less encounters (with friends and foes) for the party on the way to the battle with Tiamat and then, based on how long the party took to get there, the intervention at that point of allies and enemies.
Best Answer
This adventure takes a lot of forethought.
As the DM it falls on you to decide how much you want to either adapt your world to the players and how much you want to allow the players to change the world.
For example, you may have already decided that Tiamat is not ever going to rise in your world. You may either "redo" or otherwise give the PCs another chance at an asset they have failed to acquire. For example (no spoilers here), the PCs could need to save a village from an attack by a band of lizardmen. As a reward (unknown to them), they will be given the Amulet of Gygax, a key asset to advancing the story. Due to poor luck, and poor decisions, the lizardmen win and the PCs retreat. Rather than simply saying, "Well, you think you should try again, right?" or something along those lines, you could say, "That village is destroyed; as you lick your wounds, the lizardmen appear to be sending scouting parties down to the next village."
If you've decided that the PCs can affect the world, you might decide that the final battle is inevitable, but the PCs' success isn't. At that point, the campaign becomes one of surviving in occupied territory (and maybe plotting an overthrow).
The three items you ask about really boil down to a question (I think) of "How can I make this story fun for the players without railroading them?"
The biggest piece of guidance I can think of on that is to talk to your players about where they think they are in the game: "So Bob and I are preparing for the return of Lolth so when Tiamat shows up we'll have an ally."
Remember that this is a collaborative effort.