Pictish Slaughter

The Pictish slaughter of the SPQR refers to an event on AA where, aligning themselves with a treacherous flamen, the picts managed to sneak through the sewers and catacombs of the Roman colony before promptly slaughtering many Roman citizens, including clerks and the praefectus vigilum. 
A flamen that had dedicated his life to the worship of Pluto had been put in charge of constructing the city's catacombs. However he combined them with the use of secret passageways in and out of the city and into the sewer system that ran the length of the colony. The Picts managed to persuade him to let them use this system to enter the city. Coming out directly into the forum the pictish warband slaughtered all the vigiles and citizens present in the area. Eventually a warning made it's way to the Castrum on the outskirts of the town and the surviving citizens escaped there to look for refuge. What ensued was a battle (primarily missile based combat) between the castrum held by the legio and the colony held by the picts. Eventually the picts held out long enough to break into the treasury and with their loot, escaped the city the way they came in. 
The tunnels were not discovered by the Romans (only by OOC admins) and the picts began to be seen as evil beings able to apparate inside the city walls themselves by the local populace.