From Digibutterpwiki

Blockworld is, as its name implies, a world made up of and populated by blocks. Notable residents include ? Block and POW Block.

[edit] Plot 1

In Plot 1, ? Block headed back to his homeland of Blockworld in order to rally support from his species. They all came with him to fight Mr I, but the world itself was later destroyed.

[edit] Plot 2

In Plot 2, ? Block returned to Blockworld in search of the W and B Blocks. After he found them, it didn't have much of a role anymore.