When a life spirit fuses with a small rock, a rock golem is created. However, when a powerful spirit fuses with a large rock, like say nine feet in diameter (minimum) for the chest rock, a Boulder golem, or simply "Big Brother" is created. They are much more powerful than rock golems, and are much more destructive. Boulder golems smash anything and everything in their path that obscures their path when they've spotted a threat, and live on the ground of Rock golem forests to protect them. I haven't colored this one yet, but I might.