(Passive) worst of WIS and CON
  Possessed By: Some Humans, Lizardfolk, Grey Elves, Black Orcs, Bards, Druids, Mages, Paladins, Priests, Alienists, Earthsingers, Loremasters, Master Archers, Sentinels, Twilight Huntsmen.
  Effects:  The Concentration skill has these applications:
   * Cast while Distracted (Passive): The primary function of the Concentration skill is being able to cast spells successfully while in difficult circumstances. Every point of Concentration rating above +5 cancels a 5% increase is spell failure chance due to status conditions or enviornment. Multiple distractions form a culmulative spellcasting penalty that Concentration is subtracted from as a whole -- it isn't counted seperately against each penalty, so strong Concentration rating can be very valuable to melee spellcasters. The following situations all impose penalties to spellcasting:
   Attacks: Spellcasting in melee provokes attacks of opportunity unless the Defensive Spell feat is used; if these attacks inflict damage on the caster, his spell may be disrupted. Every 1% of the caster's total hit points lost to these attacks adds a 3% chance of spell failure, so a caster who loses 20% of his hit points to an attack of opportunity from spellcasting also suffers a -60% chance of spell success.
   Stunning/Nausea: A stunned or nauseated character suffers a -50% chance of spell success.
   Confusion: A confused character suffers a -75% chance to spell success, and if they suffer spell failure, the spell may have an odd or unintended effect.
   Grappling/Stuck: A character locked in a grapple suffers a -30% spell success chance (assuming use of the Still Spell feat, without which a Grappled character cannot cast at all), and a character that has become stuck (such as from a web spell or the strands from a tanglefoot bag) suffers a -20% chance of spell success.
   Distraction: A caster successfully distracted by a use of the Bluff skill suffers a spell success penalty equal to 5% per two points the Bluff check exceeded the spellcaster's distraction DC.
   Terrain: Swimming or being waist-deep in mud grants a -15% penalty to spell success.
   Hunger: Being Starving inflicts a -15% spell success penalty, and being Weak from hunger increases that penalty to -30%.
   Spell Effects: Spells such as insect plague, control winds or hideous laughter penalize spellcasting as described under the spell in question.
   Flight: Characters who are levitating or flying suffer a -15% penalty to spellcasting.
   Note that Concentration does not cancel penalties to spell success chance from wearing armour, low Intelligence or fighting defensively.
   * Reduce Penalties (Passive): An exceptional Concentration skill gives a character a heightened ability to resist pain, and a high Concentration skill will lessen the attack and damage penalties inflicted by magical effects that cause pain, such as pain touch, weapons of pain or a symbol of pain. If a character has Concentration as a class skill and a rating of +10, the sum of all her pain penalties are reduced by 1; at +12, this increases to 2, at +14, 3, at +16, 4, and so forth.
   * Contests of Will (Passive): Some spells and magical items (notably spiritwrack and the various planar conjuration spells) require the caster to engage in a contest of wills with another creature, which is resolved an opposed Concentration check -- whichever character scores higher wins.
   * Break Paralysis (Passive): Characters with a 15+ rating in Concentration are able to overcome paralysis effects through sheer force of will. If they fail a saving throw against a paralysis effect, they receive an additional Fortitude save against DC 18 every turn until they have beaten the effect.
   Characters with this ability are also able to move when paralyzed and truly, deeply desperate just enough that they cannot be subjected to the Coup de Grace maneuver.
   The Escape Artist skill can also provide this benefit.
   * Attack while Nauseated (Passive): Characters with a rating of 10+ in Concentration have a chance to attack even while Nauseated -- a state which normally prevents a character from attacking. A DC 20 Concentration check is required, and failing this check costs the character a full 40 segments without any action being taken, and provokes an attack of opportunity.
   * Psionic Focus (Active, Unimplemented): When a character is not in combat and not in the immediate presence of hostile creatures, she may spend a fatigue point and make a Concentration check (DC 15) to gain a state of psionic focus (which can be expended to augment psionic powers in various ways, fulfilling a vaguely similar role to metamagic for spellcasters). Failure causes the fatigue point to be wasted, but the attempt can be made freely again on the character's next turn without any further penalty.
   * Train Wisdom (Passive): The techniques of meditation and mental focus a character learns in developing the Concentration skill serve as an excelent springboard for heightening perception and strengthening the will overall. Concentration can be used to train the Wisdom attribute in the same manner that Athletics is used to train the three physical attributes.