They are weak against Golden Oriole, Grapeshot, Draconid Oil, Aard.
Contrary to popular belief, baslisks cannot turn anything to stone with their gaze. That is a small comfort, however, given that their acid, venom, claws and teeth provide them many other ways to kill.
When fighting basilisks, however, your priorities can change slightly. These scaly creatures can poison you with each and every attack, so it may be a good idea to counteract this with the golden oriole potion, which makes you invulnerable to poisoning for a decent length of time. Basilisks can also spit venom while hovering in the air, but it's fortunately not very accurate. If you see the beast take flight and stay in one place, be ready to hop to one side to avoid the incoming venom.