Caltrops may also known as caltraps, galtrops, cheval traps, galthraps, galtraps, calthrops, jackrocks or crow's feet. The name literally means "foot trap". It is an antipersonnel weapon made up of two or more sharp nails or spines arranged in such a manner that one of them always points upward from a stable base like a tetrahedron. Caltrops serve to slow the advance of mounted military units on horses, war elephants, and camels, as well as foot soldiers.
In more modern settings, caltrops are still effective when used against wheeled vehicles with pneumatic tires.
Caltrops are generally sold in 1 pound bags, though most caltrops are relatively small, fitting in the palm of the hand. Each bag is enough to cover a 2m square area.
Caltrops give movement skills a -10 if on the ground.
Each round a character is in the area of effect for the caltrops, they roll their ground movement skill check vs. a DS of 20. If they fail, they take 1d10 damage and a further -10 on their ground movement skills.