The Party bickers a while before settling on raiding a nearby tower with the intent of slaying it's masters and taking ownership of the fortification.
The party had previously raided the tower, slew the guardian beast, trashed the living quarters, and stole 7,000 gp and five bottles of expensive Earth Whiskey. By now the tower masters had hired some guards from their nearby allies
While the party observes the tower at dawn they see a group of soldiers from the nearby allies of the tower-masters visiting the tower at dawn to perform a changeover of the garrison of hired guards.
During the night they invisibly snuck up close to the tower and sent the thief to scout it out.
I make a roll on my Random NPC Trait table, to determine the "personality" of one of the guards, and come up with the result of "Does not travel during the night due to fear of Nightgaunts."
Improvising with these factors I tell the thief that he hears someone saying "I wish they didn't make us travel to the tower before sunrise, we could get taken by Nightgaunts"
Another Voice: "Don't be ridiculous, that's never going to happen. Do you know anyone who has seen Nightgaunts?"
"We don't know anyone who has seen a Nightgaunt because they come for you in the dark, and besides once you see them it's already too late!"
"You're a fucking idiot, do you know that! Shut up and listen for intruders."
The thief returns to the party and they discuss how they could manipulate the guard's fear of Nightgaunts to their advantage.
At this point my mind starts racing as I imagine the players coming up with some madcap scheme involving improvised nightgaunt costumes, illusions, sound effects, tickling and I get really excited and maybe even pee myself a bit.
The entire party attempts to invisibly sneak up on the tower.
One of the guards: "We can hear your armor intruders! Go away, there's lots of us and we're well armed!"
One of the players to me "I take out my waterskin and shake it..."
Me: "...you shake your waterskin?"
The player "It's the only thing I have that I could flap to make the sound of a Nightgaunt's wings. I wish I had a cape..."
Me: "Your waterskin..slooshes."
The Guard to another guard: "I hear them drinking water!" to the party "Yeah, well we've got water too! Fresh, purified water that's way better than your water!"