the Spider: the will as the web the Disease spins in
your personal will is the web your Disease sits and spins in, still. The will you call your own ceased to be yours as of who knows how many Substance-drenched years ago. It’s now shot through with the spidered fibrosis of your Disease. His own experience’s term for the Disease is: The Spider. You have to Starve The Spider: you have to surrender your will.
Context
The theme's core model of why surrender, not willpower, is the only cure. The addict's instinct is to fight the Disease with resolve, but resolve is issued by a will that has already been colonized — "the web your Disease sits and spins in" — so every act of self-directed will feeds the very thing it means to fight. Hence the counterintuitive prescription: you cannot out-will the Spider, you can only Starve it by surrendering the will it lives in. This is the mechanism under every "musts"-less suggestion in the scene: recovery requires giving up the faculty that addiction has quietly repurposed against you.