Long before the door opened, Kate had reservations about the door. There was more ambient blue around than she liked, and some very odd signals that were difficult to attribute simply to their being in Sigil. Moments before the door opened, her instincts screamed at her to MOVE.
And then Excalibur was in her hand, the door flew open, and a pit fiend was barreling at her - only to be slammed into the wall by Invisible Air's ("See? It is useful!" 'Point proven.') release. Kate grinned slightly. "I don't even have to feel bad about killing you!" She readjusted her grip after the wind blast and lunged.