Its a year late, but to answer H@ngar's question, the Fool's Idol is unkillable unless you slay a specific Dregling seated at the top of the Church before you go dwn to fight it. That's because the Dregling is protecting a special doll that is the true form of the Fool's Idol's soul. Given Alice's power to control dolls and the fact that the Fool's Idol is actually a demonic doll, it naturally seems lik a match made in Hell.
