They're with the band.
Moloch von Zinzer and seven former Castle Heterodyne inmates travel through Mechanicsburg during the Baron's assault on the city, making repairs under the direction of the Castle. Moloch refers to the group by name here ✣ . Members of the band are:
- R79 - A spark-crafted minion
- Squinaldo - A spark
- Doctor Mittelmind - A spark
- Fräulein Snaug - A spark-influenced minion
- Professor Mezzasalma - A spark
- Sanaa Tryggvassen - An elected pirate queen
- Thanos the Wrenchman - A minion who transferred his allegiance to Agatha, and is possibly a native citizen of Mechanicsburg.
Moloch von Zinzer is the leader of the Band and begins to realize that he is Agatha's Chief Minion, with the responsibilities and privileges that entails, although he is mostly strongly in denial about this fact.
They are presumably still making repairs when the Baron descends and activates his Take-Five Bomb, but this has not been shown in-person, and any or all of the group could in theory have escaped the city before it was time-frozen.