Pravuil is a Denizen who used to work in the Coal Cellers of Mister Monday.
Under Mister Monday
Pravuil was a coal-collector in the Coal Cellars. He and Suzy Turquiose Blue are in a fight as Arthur finds Mister Minday to claim the key. It seems that he might be spying for a trustee.
Under Sir Thursday
Pravuil reappears as Major Pravuil and delivers the unprecedented orders to simultaneously open all 4 gates between the void and the edge of the great maze, allowing in the Piper's army of Newniths. It is likely this order did not come from Sir Thursday and so we cannot be sure who Pravuil is actually working for, although it appears likely that he is on the side of the Piper.
Under Superior Saturday
Pravuil is shown to be an important figure, being addressed by name by Superior Saturday.