The Jack O' Block is a special Halloween item. It is one of the prizes Growganoth can give for a sacrifice of rarity 15 or higher. It can also be obtained by fishing using the Halloween themed baits ( Lesser Otherworldy Bait, Minor Otherworldy Bait, etc.) even when it's not Halloween. It is a solid block. There are two other variations that can be obtained from Growganoth: Pumpkin Block and Lit Jack O' Block.