The most characteristic feature of the basilisk is its ability to kill at a distance, either with venom or a glance. Its glance would kill instantly and its breath could break stone. It was formerly believed that if killed by a spear from on horseback the power of the poison conducted through the weapon killed not only the rider, but the horse also.
Weasels can bite Basilisk to death. Men put them into the caves where the basilisks lie hidden. The basilisk might look daggers, the weasel cared not, but advanced boldly to the conflict. When bitten, the weasel retired for a moment to eat some rue, which was the only plant the basilisks could not wither, returned with renewed strength and soundness to the charge, and never left the enemy till he was stretched dead on the plain.
Those who went to hunt the basilisk took with them a mirror, which reflected back the deadly glare upon its author, and by a kind of poetical justice slew the basilisk with his own weapon.
According to some tales, the crowing of a cock can also kill a basilisk. This weakness also affects other monsters like faeries, ghosts or vampires that are supposed to appear in the night and disappear at the first light.
The basilisk was of some use after death. Thus we read that its carcass was suspended in the temple of Apollo, and in private houses, as a sovereign remedy against spiders, and that it was also hung up in the temple of Diana, for which reason no swallow ever dared enter the sacred place.
It was also said in antiquity that silver rubbed with the ashes of a dead basilisk would make the silver take on the appearance of gold. These protoscientific uses of the basilisk persist in the medieval bestiaries and the latter attribute became quite popular in the alchemical tracts of the Renaissance.