Here's some info about how common character conditions are processed in the game:
Blinded: A blinded creature's armor class decreases by 2. It also loses any dexterity bonus to armor class. Speed is decreased by 50% and the creature loses the ability to charge. Whenever the blind creature attacks an opponent, the opponent is considered to have concealment 50%. Lastly, a blinded creature cannot take AOOs (attacks of opportunity) against other creatures.
Graphical representation: a black eye icon floating over the creature.
Sleeping: A sleeping creature has been magically put into a deep state of sleep and is unable to act. The dexterity score falls to 0. The creature is considered helpless and is therefore a potential target for a coup de grace. Helpless characters victim of a melee attack suffer a penalty of -4 to their armor class. The spells Sleep, Deep slumber and Power word sleep can give this condition to a creature. If there is a friendly creature near the sleeping creature, the friend can shake the sleeping creature out of its sleep with the Wake Somebody Up standard action. A sleeping creature that takes damage is automatically woken up.
Graphical representation: “Zzz” symbols floating over the creature.
Stunned: When you are stunned, you cannot take any combat action, your armor class decreases by 2 and you lose any dexterity bonus to armor class. Spells like Sound burst, Discharge and Power word stun can give this condition to a creature.
Graphical representation: stars rotating over the creature.
Confused: Each round, a confused subject rolls to determine what it will do: Attack an enemy creature (01-10), Act normally (11-20), Do nothing (21-50), Run away (51-70), or Attack the nearest creature (71-100). The spells Confusion and Insanity can give this condition to a creature. The spell Heal can remove the condition.
Graphical representation: coloured rings floating over the creature.
Protected versus evil: This condition gives a character a bonus to armor class and to saving throws whenever he his attacked by a creature of evil alignment: lawful evil, neutral evil or chaotic evil. The character also gains immunity to mental control. The spells that give mental control over a creature are: Control Person, Control Monster, Dominate Person, Dominate Undead and Dominate Monster. You gain the Protected from evil condition with the spells Protection from evil, Mass protection from evil and Greater protection from evil. Evil creatures instead cast the spell Protection From Good and
gain bonuses when attacked by creatures of good alignment.
Graphical representation: a blue aura surrounding the creature.
Paralyzed: A paralyzed creature is frozen in place and is unable to act. The dexterity score falls to 0. The creature is considered helpless. Therefore, it is a potential target for a coup de grace. Helpless characters victim of a melee attack suffer a penalty of -4 to their armor class. A paralyzed spellcaster can still cast spells with no somatic component (use the Metamagic Still feat). A paralyzed monster can still use its Breath weapon. Some creatures, like the Ghoul, have a special attack that paralyzes the victim. The spells Ghoul touch, Hold person, Mass hold person, Hold Monster and Mass hold monster can also paralyze a creature. When the paralysis originates from a “Hold” spell, the victim can attempt to Break Free every round as a full-round action. This requires a successful Willpower saving throw.
Graphical representation: blue rings around the creature’s waist line.
Nauseated: Creatures with this condition are unable to cast spells or attack. Nauseated characters can still move. The maximum distance moved in a round is equal to the character's speed. The spell Heal can remove the condition.
Graphical representation: the creature turns green.
Invisible: When you are invisible, you gain a +2 bonus on Attack Rolls when fighting against sighted opponents. When you attack them, sighted opponents also lose their dexterity bonus to armor class if they had one. If the creature you attack is blind, has the True Seeing condition, Can See Invisible ability, Blindsight ability or the Blindfight feat, you do not gain these bonuses. Lastly, when invisible you gain concealment 50% and enemies cannot take AOOs against you. If you received the invisible condition from the level-2 Invisibility spell, you lose the condition as soon as you attack someone or cast an offensive spell.
Graphical representation: the creature becomes transparent.
Enlarged: A character can gain this condition from the spell Enlarge person. The condition brings the following effects: strength increases by 2 (size bonus), dexterity decreases by 2 (size penalty), the armor class decreases by 1 (size penalty), Attack Rolls decrease by 1 (size penalty). Damage Rolls increase greatly as the weapon's size category increases by one.
Graphical representation: the creature’s sprite is stretched by a factor of two.
Comments are welcome. For example, should the game allow to perform a ranged attack while blinded?