φυλακτόν
From LSJ
ἔγνω δὲ φώρ τε φῶρα καὶ λύκος λύκον → the thief knows the thief and the wolf knows the wolf, and thief knows thief and wolf his fellow wolf, set a thief to catch a thief
Greek (Liddell-Scott)
φυλακτόν: τό, = φυλακτήριον 2, ἐξουθενῶν τὰ λεγόμενα φυλακτὰ καὶ τοὺς λεγομένους ἐξορκισμοὺς Βίος Νείλου Νεωτ. σ. 4.