1) During their wanderings, the PCs walked right into a shambling mound when they were still only level 1. To escape, they made a deal to leave all their horses for it to eat. Unbeknownst to them, it then used the carcasses to spawn a half-dozen baby shamblers. The Stag Lord has captured one of the young ones and fed Beaky, his feral owlbear, to the baby shambler. The plant will serve a comparable role to the owlbear.
2) More recently, they cut a similar TPK-avoiding deal with a pair of will-o-wisps to feed them the fear and pain of a whole nest of bandits. They'll wreak some havoc on both sides semi-randomly.
3) Tartuk, the kobold sorcerer, escaped from the Sootscale caverns. He has since insinuated himself into the bandit hierarchy. He will be a potent, if cowardly, adversary against the PCs.
4) There are currently five soldiers of Brevoy held prisoner inside the fort as a result of the backstory of one of the PCs. If armed and liberated, they can be a useful set of allies for the heroes.
5) Last but far from least, the party druid is actually a traitor working for our favourite green-haired person. Her player has been slated to leave the city since before the campaign started. The druid has already weakened the party by persuading them to forego a trip to Oleg's for important supplies and new equipment. Once battle is started inside the fort, she will turn on the group at an appropriately dramatic moment. I've asked the player to do everything she can to make sure the character survives so I can use her later.
