Negating

A negating weapon briefly nullifies some forms of damage reduction when it damages a creature. Whenever a negating weapon damages a foe with DR/chaotic, DR/evil, DR/good, DR/lawful, or DR/magic, it reduces the value of that damage reduction by 5 points for 1 round. For example, a +1 negating lance hitting a creature with DR 10/good and lawful reduces the creature's DR to 5/good and lawful. If the creature has a component to its damage reduction other than the alignment types listed above, that component is unaffected. Thus, if the +1 negating lance above hits a demon with DR 10/good and cold iron, it would leave the demon with DR 10/cold iron and 5/good for 1 round. The effects of multiple negating weapons (or multiple hits from the same weapon) do not stack. This ability can only be placed on melee weapons.