@Sombrero
Something tells me that the dark silhouette is gonna be a new player. If not, whoever decides to mess with a mage, a gunslinger, an archer, a knight and a boxer ready to ambush him/her/it is gonna have a real bad day :)
You'd be surprised. Back when I had the time to go to Friday Night Pathfinder, one DM in particulary absolutely tortured us all with lone doppelgangers, lone slimes, lone bowls of spaghetti. We were always less worried about encounters that showed up in "Gangs", "Squads", "Nests", "Swarms," "Droves", or "Herds" than "So you see this one [insert thing] ambling into the room."
I mean, for gods' sakes, man, this is a Halloween rp! For all we know, this one encounter could be the means by which our individual dooms are engineered! After the interaction, we might have to test everyone's blood with fire like in The Thing!