I chose the symbols on Harry’s three throwing knives intentionally, and each matches its role later in the story. The shield is unpoisoned; it’s the one he ends up using most of the time in two-handed defenses. The dragon is poisoned with sleeping potion, as a nod to the Hogwarts "draco dormiens" motto. The Potter family motto one—"no better friend, no worse enemy"—is poisoned with basilisk venom because, well, there is no worse enemy than that knife, is there?