The Heart of the Tunnels
Up - Varisian Wanderings
It is possible for the party to disguise themselves as slaves, as long as they don't look too geared up. Also, with a darkness spell, they could pretend to be dark creepers.
Regardless of what they choose to do, there are quite a few spots where the tunnels could be collapsed. There are occasional patrols through the tunnels (on a 1 or 2 rolled on a D20 - varies for how well they roll to disguise, someone will notice that they don't belong or are up to something, at which point they will have a round or two before a trio of serpentfolk arrive.), and also slaves will report their presence. Troops of kobolds, watched by a single serpentfolk, also pass through on occasion. The closer they come to Viperwall, the more likely any activity is to provoke suspicion. If there is fighting, it is also more likely to draw others if it is closer in. If they just keep fighting their way in, then eventually, a half dragon will show up (12 rounds after the first combat). If they cause trouble in Viperwall, then it is possible that the Leader could show up also.
Patrol
A patrol is two small serpentfolk and one large.
Description of bottom level
One ramp down (on the east), splits and goes both into the basement and into the tunnels. Directly opposite it in the long hallway is a tunnel that goes off to the west.
On this level is some storage, rooms for slaves who tend the water monster, and workshops for humans working making kobold armor.