Off-Guard
An off-guard creature can't react to danger fast enough due to being unaware or unprepared.
Stage 1 (Off-guard): The off-guard creature suffers a -2 penalty to their defenses (Armor Rating, Dodge DC, Parry DC) and saving throws. All attacks against them gain the unavoidable property and they cannot take free actions or reactions outside their turn.
Stage 2 (Exposed): As stage 1 but the penalty is -3. All attacks against them are armor-piercing and they cannot benefit from Combat Reflexes, Dodge, or Evasion or similar abilities or anything that has any of these abilities as a prerequisites.
Stage 3 (Vulnerable): As stage 2 but the penalty is -4. All attacks against them automatically hit, but don't automatically crit.
Stage 4 (Helpless): As stage 2 but the penalty is -5. All attacks against them automatically hit and crit.
*If a creature is only off-guard only against certain targets, it means actions and movement taken by those targets cannot trigger the off-guard creature's free actions and reactions but they can otherwise act normally.
Note: Flat-footed, Denied Dexterity Modifier to AC, and the bonus to attacks due to being Invisible or Hidden are all replaced with this condition instead. So attacking a creature while you are hidden from them simply means they are off-guard 2 against your attack. If you're concealed from them they're only off-guard 2 and if you're undetected, they're off-guard 3.
Note that the attack bonus from Flanking still functions normally. However, a creature that is flanked by 4 or more enemies is off-guard against all attacks that successfully flank them. So 3 or less creatures flank normally but 4+ also get the benefit of an off-guard victim.
Special: Anything that would cause you to "lose your Dex bonus" or "catch you flat-footed" causes you to be off-guard. All creatures are off-guard by default at the start of any scene until their first turn starts. As all creatures have this condition, the Initiative and Perception penalty is ignored unless another creature somehow doesn't suffer it.