Old One said:Rel,
I will let Tortoise answer directly if he is so inclined, but from my perspective, I had let a couple of hints drop...
(1) The green/brown clad gnolls had shadowed them on both their trip to and from Oar, without attacking. Of course, the paranoia inspired by hard-bitten gnoll woodsmen running around your flanks and rear with huge, slavering wolves was fun...fun for ME that is!
(2) They didn't attack immediately (like every other gnoll band they have run into). It did take a big set to walk out there alone, however, since for all Rowan/Tortoise knew, they were just another, allbeit rival, gnoll band to Skilorn.
Not only did he essentially negotiate a truce with his 1st favored enemy, he also was able to get them to do the caravan and, indirectly, the party a favor by slowing down Ned Galway's crew.
~ Old One
While the hints were there it was definitely a gamble. As a player I was thinking something like this " Phil likes to keep us guessing, but he likewise likes to give us character growth opportunities. How we handle these determines how his NPC's act, therefore this could be a boon or a boondoggle. I also clearly saw this as a chance for Rowan to shine/grow. "
The trip to and from Oar made it obvious that these gnolls operated differently from their northern kin, but that didn't make them instant nice guys, just more cautious, better prepared, and judging by the sharply formed lines and the leashed war wolves, capable of deadly organization.
I figured we were far too outnumbered for this to be planned as a fight unless we got stupid. If we let them come to us they would set all the terms for what was coming. If we took some initiative it might break up the routine and give us a chance to find the "out" we perceived was needed.
Some in-character thoughts:
"Either they've been called to help the other gnolls or they're here to fight the other gnolls. I really hope the latter."
"Maybe if we show them we're willing to go down fighting and show them we've already handed the other gnolls a bloody defeat they'll hesitate and reconsider, not knowing just how much fight we have left in us. I hope I can pull off this bluff or we're done."
"Wait ... that symbol on his armor ... it's a slight variation on one of Corelian's marks ... gnolls worshipping the light? What're the chances of that?"
One thing lead to another and the discussion went from "Is Skilorn dead?" to "We have seen you, walker in the forests, do we have your promise that the others will do no harm ... ?" to "We will send a wolf to the ridgeline to howl three times if we agree to your plan for the other caravan.You may take your horses and return to your companions."
Ah, the visual of Rowan leading the horses back to camp from amid an army of gnolls, unharmed.

The wolf came, and the rest is history. Poor Ned, I hope he soiled his breeches when these gnolls and their big bad wolves harrassed his theiving brigands all the way to the river staying just out of harms reach the whole time.

Oh how bigotry falls aside in the face of unexpected realities.

As a player I'm now looking for a chance for Rowan to go south and study with these gnolls a bit and then convince them to send help further north to help with *spoiler*.
Can you tell I had a blast with that session as a player? Awesome stuff. Old One can really weave character developement into the campaign very well. I'm OK as a roleplayer (not great, just OK), but I have been able to throw myself into this role deep at times. That session was one of those golden moments.