Physical description and makingEdit
They were clean cuts that allowed the traveller to slip through into another world. They could travel into different terrains, underground, underwater and in the air. They could be made by the bearer of the subtle knife focusing had to open loops in the multiverse and so creating windows.
Serafina Pekkala told Will Parry's dæmon Kirjava and Pantalaimon, Lyra Silvertongue's dæmon that she would close all windows in the universes except the one in the land of the dead because all of the Dust that was flowing out of these windows, destroying the worlds. As well as that, every window opened by the subtle knife caused a Spectre to appear which is why the world of Cittàgazze was full of them, once every window was closed, Xaphania said that the angels would take care of the Spectres.