"The Stone Slammer is a heavy-duty, flying mountain that targets defensive buildings by flattening them with giant boulders and causes earthquakes. Immune to spell effects." The Stone Slammer is the third Siege Machine you unlock, available when the Workshop is upgraded to level 3. The Stone Slammer can be described as an incredibly high hitpoints, high damaging Balloon, as it shares the Balloon's relatively slow movement speed and high damage with low attack speed, as well as defense targeting.