Boss Block

Boss Blocks are a type of obstacle in Tunnels from Nowhere. They are wide barricading bricks of multiple colours with an engraving in the middle, symbolizing their respective boss. When that boss is defeated, their blocks globally become transparent, only remaining as dotted lines to indicate where they were. Open boss blocks give way to new progression and secret areas.

The behaviour of these blocks is comparable to how Switch Palaces and dotted-line blocks in Super Mario World function, although those are not mandatory for completion.