Regarding Invisibility

In the many years that I have played RPG and other games, one of the most difficult to balance and implement, without making it either too powerful or too weak for either the player group or the NPCs, has always been Invisibility.  Each game has its own definitions of how to implement, how to use, and how to defeat such an ability, but it almost always leads to problems.  Either the players take advantage of the power, or the NPCs are too strong, or invisibility is made so ineffective as to be nearly worthless.

For the most part, everyone understands the basics – invisibility prevents you from being seen, which means it is difficult target or interact with an invisible character.  The problem comes from how difficult “difficult” is supposed to be.

In the Hero System, Invisibility is a basic power, that gives you freedom from the more common targeting sense Sight.  Although you are aware of an invisible foe (assuming noise or other clues), you cannot target except with halved skill levels or other modifiers.  You can instead use area-of-effect attacks, indirect attacks, or other targeting senses to engage with the target.  But the rules dont really give a clean way to track an invisible foe – ie, if you are using miniatures, then there is a sense that the enemy is in a specific spot, even if the character cant see them, making targeting relatively easy.  If the foe is not tracked, then there are concerns about the invisibility being too powerful, as no one can locate them.  No easy middle-ground.

In the Pathfinder system, the situation is very similar.  There are no targeting senses, but instead everything depends on Perception skill.  The game system also heavily uses miniatures, and a very rigid turn sequence, which makes an invisible character problematic.  If the figure is left on the board, it tends to be easy to predict viable options for movement and location.  If figures are not used, then it is too easy to lose track and “overpower” the ability.

In concept, the mechanics make the situation pretty straightforward – roll a perception check to detect and if appropriate, pin-point an invisible foe.  In practice however, it tends to be much more problematic.  What is the perception check DC?  Is it -10, foe hearing a foe in combat?  Is it 10, for a foe in combat, but adding the Invisibility +10?  What if the foe steps back and opts to stand still, or uses stealth to move away?  Once spotted and aware of the invisible foe, what then is needed to pinpoint the foe, and make a directed attack?  And if miniatures are used, what prevents the character from simply walking up to the known and predictable location, and making an attack?  Or tossing a fireball or AOE into the area to blast them?

In truth, the rulebook goes into great detail on the situation, and likely I simply cant understand all the ins and outs of the process.  But in practice, my gaming groups have debated the what-ifs endlessly, and never really come up with a logical solution that satisfies all sides.

As a result, I submit the following alternate suggestion and solution.  This is a basic process which I actually developed on a whim during a Cypher game, when the group encountered invisibility.  Basically, leave the miniature on the board, and move it around normally like a visible character.  This assumes the group is aware of an invisible foe, if not, then most of this is irrelevant.  Since the foe has a visible miniature, obviously everyone has some sense of where the foe is located.  Which isnt too far from reality in that most people can hear someone walking, etc, nearby.  The difference comes in when the foe is attacked.  In this case the process we used was a bit of a gamble for the character – first the character declared his attack or action vs the invisible foe.  If it was an AOE or non-targetted ability, it was subject to GM discretion as to if the foe was in the effect.  If the attack is a targeted attack, then an immediate Perception check is necessary.  In Pathfinder mechanics, the DC is simply 10+ the Stealth skill of the foe.  If the foe is actively stealthing (or did last turn), the DC is d20+Stealth +20.  In either case, the character rolls their normal d20+Perception for their check.

The intent is that someone who is invisible but interacting makes noise, but has an inherent “quietness” (ie, their Stealth level).  A rogue will naturally be quieter than a heavy armor Fighter, regardless of if they are actively trying to be quiet.  Thus the DC of Stealth+10 for Invisibility (not the full +20, since vision is only one way to detect the foe).  Someone who is intentionally attempting to avoid noise and be quiet (ie, active Stealth), gains the game mechanic of the +20 to invisibility, thus Stealth skill +d20 +20 (full invisibility bonus).  That represents actively being stealthy.  The concept would be that attempting to hear a non-invisible person would be a 0, plus arguably any natural quietness.  To hear a stealthing character, it would be 0+d20+Stealth (ie, a Stealth check).  Then we simply apply the Invisibility bonus of +20 (or only +10 for “passive” stealth).

As an example, assume a Rogue (+8 Stealth) and a Fighter (+0 Stealth).  Both are invisible, and facing a Wizard (+5 Perception).  If the Rogue and Fighter simply move about the room, engage in combat, interact, etc, they have a 18 and 10 DC to be “spotted”, assuming the Wizard is aware of their presence to begin with.  If the Rogue and Fighter actively stealth, the DC rises to 28+d20 and 20+d20 respectively.  In all cases, it would be modified by range (-1 per 10 feet) as is normal for Perception.

Once the result of the Perception check is determined (either success or failure), then the action of the character is resolved.  If it is a success, then the attack happens normally – the foe can be targeted by direct spells and attacks, etc. (subject to the normal 50% concealment chance of Invisibility).  If the Perception check is a failure however, then the attack automatically fails.  The spell or action can be cancelled or completed as desired by the character, but regardless the Standard Action is used, and the foe is not in the expected location, thus suffers no effect.

The net effect of this is that the game can move along quickly, without worrying about removing characters from the board, since their location becomes more of an indication, rather than a true physical location.

Ultimately, this all may be how the Paizo writers of Pathfinder intended Invisibility to work, and we simply have overthought the situation.  But for at least my current group of newer players, this solution seems to be workable and consistent.