Opening Scene:
PCs are at the temple paying respects (those who explicitly don't want to be followers of Bahamut, maybe they are there are friends of another PC and just sitting and waiting for that other PC to say his prayers)
There is also an elderly dragonborn priest there -- an important high priest who is said to hear whispers from Bahamut's angel messengers.
All is quiet until there is a loud shout outside in the distance.
The temple door is kicked open and it is a paladin soldier of the abbey "The outer wall is being breached. You five (pointing to the PCs), get his holiness out of here. If he is injured or killed, we shall never know the prophecy he has been interpreting... you you and you (pointing to other random people) get to the halls of glory and begin moving some of the relics in to hiding."
Here is a run through idea for a prequel session, put in sblocks because i do mention a couple things as foreshadowing that might spoil a couple surprises.
Encounter 1:
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Skill challenge. PCs must convince the high priest to come for the interest of the faith as a whole
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Encounter 2:
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The high priest needs his prayer book to finish interpreting the prophecies, it's at the dormitories. The PCs much take him and get the book. However, some of harpies are in the dorms. Fight through them to get the priest's book. As a subtle foreshadow, as the PCs are leaving the dorms, mention that they see a few more harpies that are flying in the distance nearby.
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Interlude to set some scene
[sblock]
Exiting the dorms, the PCs run in to Captain Havarr. He sees what they are doing and explains to them that the main path out is too dangerous and that they should use the secret staircase. The high priest makes some cryptic comment to Havarr about how he needs to make wise command decisions and remember the grand scheme rather than immediate repercussions (of course, havarr (not knowing what he is about to actually do) thinks that the high priest is just commenting about general fighting command decisions and not the other decisions he is about to make).
Taking the priest to the secret stair case becomes a problem as the priest says he is too feeble to go that way (yes, i know the secret stairs is supposed to not be a challenge for the PCs in "madness" but let's say it's too difficult for this old man. and it's not exactly the type of thing they can carry him down ...)
So he says "But you did convince me I need to leave -- so let us make a hard push for the lower area"
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Encounter 3:
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Heading towards the lower area, crossing through the grove, there is a bear (or some other natural creature) that is simply spooked by all the commotion and and is being predatory in an effort to protect its bear cubs.
note that the fighting is still mostly at the lower area right now and not crossed into the groves. so play up the sound of fighting as they get further and further down into the lower area.
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Encounter 4:
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The party is more or less surrounded by fighting of orcs and paladins now. Skill challenge on how to get the priest through.
success allows them to make progress and the priest has time to cast a bless on them (+1 to all attack rolls in the next encounter)
failure should just result in a skirmish with some orcs but otherwise they still make progress but no bless from the priest
[/sblock]
Interlude to set some scene
[sblock]
Play up how they are seeing lots of fighting going on. At one point they can see many people dieing on both sides. Also mention a touching scene of a man in long blue robes (Vandomar if any of the PCs are from the abbey and would know him) carrying a corpse up the staircase and into his tower as he ignores the flaming arrows being shot around him.
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Encounter 5:
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In a corner ally, the party sees a paladin being attacked by orcs. He'll surely be killed if the party doesn't stop. They have the option of trying to rescue him (despite needing to get the priest out quickly and safetly) or just keep going.
If they fight and rescue the paladin, it's Silas - he got separated and he must hurry off to the garrison
If they don't fight / rescue him, pretend that this is Hrom (who in the original history never made it back to the garrison).
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Encounter 6:
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The party can either try and scale the wall with the priest to get out or head for the main gate.
In either case, as they do so, they are caught by the orc second in command and his troops
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Encounter 7:
[sblock]
After the PCs get out with the priest, there is a final encounter with some other random creature (we'll say werewolves). They were allied with the orcs and are coming as the orcs reinforcements. The PCs here have a chance to stop them and keep the werewolves (or whatever creature) from actually being part of the invasion force (since the events of "Madness" don't have the werewolves).
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And, of course, during encounters 1-7, the priest needs to be kept alive. And there isn't really any directions the priest could go run and hide since you go too far one direction and he's bound to attract the attention of more orcs/etc. so in different encounters he might very well be standing in the middle which changes PC tactics some
Closing
[sblock]
as the PCs finish encounter 7 or 6 or whatever you decide to do, the sky fills with dark clouds and multicolored lightning begins to flash all around the inside of the abbey walls.
The PCs feel blinded by the flashes of light, the last thing they remember is the priest casting some sort of protective spell and invoking the name of bahamut.
You can end it there. Or if you want to use the same PCs for Madness, the PCs then wake up 10 years later in Winterhaven. They are told that they have been in a coma all this time but the high priest had saved them.
The high priest has since left winterhaven and has translated many important prophecies in the 10 years since. so it is a good thing that he was saved. the PCs can be brought up to speed about what has happened in the past 10 years (chaos just seemed to settle in at the abbey and anyone who tries to go there is never heard from again ...)
this then leads to lord padrig learning that the coma patients have awoken. he is interested to speak with them as they are the only living people who were at the abbey (aside from the priest they saved). given their knowledge of the place, they want the PCs to try and go and investigate since the abbey has become a base for the orcs who seem to closer and closer to winterhaven as their supplies run around. it's not safe...
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Obviously, i added a bit more than what could be done in a single session since you might want to trim a way some of these encounters if they don't fit your group's playstyle.
okay, sorry that this is a ramble rather than something more coherent. This is really off the top of my head so I didn't give it full thought.
The other things I would add in general is, for any sort of prequel, remember that at this point of the prequel, [sblock]it should mostly just be an orc invasion at the lower area. most of the other things at the abbey are a result of what happened after "the event"that Havarr did.[/sblock]
