Catapult Explosions. The Siege (Expansion) Once upon a time, two powerful families fought side by side to withstand intruders plundering their land. The siege lasted days, weeks, and then months, increasingly dividing the allies. Conflict is in the air... Siege is the fan-anticipated expansion to Catapult Blast. Combine Blast Catapults and Siege expansion components. With this option, you can battle with 2–4 players. The add-on brings additional weapons into the game, new knight figures, and more items to expand your castle. With the Siege variant, you can build a monumental fortress, but don't be fooled by appearances! Allies can turn on you!.