Conjuration (Creation)
Level: Sorcerer/wizard 0
Components: V, S
Casting Time: 1 standard action
Range: Close (25 ft. + 5 ft./2 levels)
Area: See text
Duration: 1 round/level
Saving Throw: None
Spell Resistance: No

You speak the words and spread your palm open, as if you were throwing jacks. Coppery sparks spring from your palm, filling the corridor with small four-pronged spikes.

A caltrops spell covers one 5-foot-by-5-foot square with caltrops. Every time a creature moves into an area covered by caltrops or spends a round fighting while standing in such an area, it might step on one. The caltrops make one attack roll (+0 melee) against the creature. For this attack, the target’s shield and deflection bonuses do not count, nor does its armor bonus for armor worn. A target wearing shoes or other footwear gains a +2 armor bonus to Armor Class (which does count). If the caltrops succeed on the attack, the creature has stepped on one.

A successful attack by a caltrop deals 1 point of damage. If the target is Small, Medium, or Large, its land speed is reduced by one-half because of the injury. This movement penalty lasts for 24 hours, until the creature is successfully treated with a DC 15 Heal check, or until it receives at least 1 point of magical healing. 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 or opponents outside the size range given above. A giant centipede, for example, can scramble among the caltrops with no chance of hurting itself, and a fire giant wearing thick, massive boots might be immune to their attacks.

For every two caster levels beyond 1st, you can affect an additional 5-foot-by-5-foot square, and the caltrops’ attack bonus increases by 1. Thus, you affect two squares at 3rd level (+1 melee), three at 5th level (+2 melee), four at 7th level (+3 melee), and a maximum of five at 9th
level or higher (+4 melee maximum).

Multiple caltrops spells (or mundane caltrops) occupying the same space have no additional effect.

(SpC, Page 42-43)