The aurora borealis, also known as the northern lights, is a natural light display in the sky of the Earth's Arctic regions, caused by the collision of energetic charged particles with atoms in the Earth's thermosphere.
Sometime during her career as a hypnotist, the Contessa discovered a a way
The Northern Lights were basically used to hypnotise everyone who had eaten food covered in spice. Arpeggio planned a lightshow in order to complete this plan, by using his bilmp.
If Sly ,Bentley and Murray didn't overload the battery charger, the silo, located near the lighthouse, would have been filled with the light energy and therefore would be collected by Arpeggio's Blimp.