Boulder
From Dark Castle Wiki
Boulders are one of the more common Obstacles, and have appeared in a few of the levels in the Dark Castle Series, some of which are Fireball 3 and Black Knight 2, Shield 1. They are not Enemies, but more Obstacles. They are thrown by the Rock Henchman, and will bounce around until the leave the screen.
[edit] Strategy
The best strategy is to move quickly, and try to jump over, or duck under the rocks. The Shield can be extremely useful against these.
