Iron Stake

This spell creates a 1-foot-long spike of cold iron that you fling at your target as a ranged touch attack. the stake is treated as a magic and cold iron weapon for the purpose of overcoming damage reduction, and deals 1d6 points of piercing damage for every 2 caster levels you have (maximum 10d6 at 20th level).

Additionally, if a creature with DR/cold iron takes damage from this spell, it is sickened for 1 round and must attempt a Fortitude save. If it fails, for a number of rounds equal to your caster level, it must succeed at a concentration check (in addition to any normally required concentration checks) to use any spells or spell-like abilities it has—the DC of this check is equal to 15 + twice the spell’s level. If the creature fails this concentration check, its spell is wasted.