Mix spiders into alcohol to make acid. Spiders have a little bit in them already, but if you really want to make it potent, smash them in some whiskey to make a deadly acid that will rip through anything.
You're trying to find a container for this acid when Santa-san (さん) bursts through your wall. He frowns down at you. You're on the naughty list now. You killed spiders AND made dangerous acid? Ooooh you're in trouble.