The queen guards d4 from four directions, but is shut off by a pawn each time. In critical play a piece crosses over a square on which there follows an interference. In pericritical play the piece moves round the critical square rather than crossing over it.
Satanick Mukhuty: Excellent peri-critical decoy of the black queen in three thematic variations. 1...Qg7 and 1...Qg4 are more interesting, being connected to logical tries.