My group's about to confront the beholder in the far realmed up watchtower and assuming they win, the watchtower reverts to normal and the adventure presents a skill challenge/combat encounter in which the PCs join mercenaries to defend it from the orc forces. Which is all well and good and a good time will be had by all, except how in the blue hell do mercenaries get to the tower in the first place? That and the original design for said tower is presumably to defend against threats that are outside the walls and the orcs are in the village within. I don't need anything too detailed, just something that passes the refrigerator test.