The Gargoyle's Touch is a power possessed by the Demon Warlocks, giving the ability to turn beings into stone. Qwan used it to attempt to save himself and his five companions, also warlocks, but he was the only survivor.
This ability is done by sending a surge of magic from the mind to the object, therefore turning it into stone. It was first used in The Lost Colony.
Used by N°1 in The Lost Colony (its first time mentioned in the series) when attacking Leon Abbot, he turned his odd weapon choice of a skewer into stone, ripping of Abbot's plated armor (which Abbot secretly healed). It is unknown whether demon warlocks are the only fairies possessing this talent, though it seems Artemis knew what it was, possibly from reading the book. It also seems that no other fairies have performed this in the series but Qwan and N°1.
Qwan used this tool to turn himself and his apprentices into stone when they were blasted into space and time.