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Caltrops resemble large metal jacks with sharpened points rather than balls on the ends of their arms. They are essentially iron spikes designed so that one point is always facing up. Scatter them on the ground in the hope that enemies step on them or are at least forced to slow down to avoid them. One bag of caltrops (the 2-pound unit listed on Table: Goods and Services) covers an area 5 feet square. Each time a creature moves into an area covered by caltrops (or spends a round fighting while standing in such an area), the creature may step on one. The caltrops make an attack roll (base attack bonus +0) against the creature. For this attack, the creature's shield, armor, and deflection bonus do not count. (Deflection averts blows as they approach, but it does not prevent a character from touching something dangerous.) If the creature is wearing shoes or other footwear, it gets a +2 armor bonus to AC. If the caltrops succeed at the attack, the creature has stepped on one. The caltrop deals 1 point of damage, and the creature's speed is reduced by one-half because its foot is wounded. This movement penalty lasts for 1 day, until the creature is successfully treated with the Heal skill (DC 15), or until it receives at least 1 point of magical curing. A charging or running creature must immediately stop if it steps on a caltrop. Any creature moving at half speed or slower can pick its way through a bed of caltrops with no trouble.
The DM judges the effectiveness of caltrops against unusual opponents.