Once, one of your pawns on files c, d, e, f may step one square diagonally forward onto an empty square. Not a capture.
You draft Revolving Door in Buff mode. Passive: it works on its own the whole time you hold it, with nothing to activate.
As a movement card, it changes how one of your pieces is allowed to move.
“Central pawns enter at an angle and act like they meant to.”