TYPES OF ILLUSION SPELLS

The are four primary types of illusion spells:

Phantasm Illusion Spells. [phantasm] These weak illusions include either a sight or sound component only; Or, if sound is included, it is indistinct. These spells cannot alter the appearance of existing creatures or environments, but can add illusory creatures or objects.

Spectral Illusion Spells. [spectral] The spells are more powerful, including sight, sound, smell, and thermal components. These spells cannot alter the appearance of existing creatures or environments, but can add illusory creatures or objects.

Seeming Illusion Spells. [seeming] These spells change an existing creature's appearance. Gear can be added, changed or taken away.

Hallucinatory Illusion Spells. [hallucination] These spells change the appearance of the environment. These spells can add, change, or take away existing objects or features.

Line of Effect and Line of Sight. While concentrating on the illusion, the caster must maintain line of effect and line of sight to the point of origin of the area of effect.

DISBELIEF

Disbelief Save. A creature's saving throw versus an illusion spell (included in the list above), is called a disbelief save: e.g. Make a Wisdom Disbelief save vs. Spell (success disbelieves). Unless otherwise specified, a successful save will cause the illusion to become transparent to the viewer. Thus, the illusion can still be seen as a ghostly image, but it is clearly not real and anything hidden or blocked by is apparent. If the illusion is sound related, the noise will take on a thin, metallic-like sound. All disbelief saves are made by the GM on behalf of the creature/character disbelieving.

• Interaction. [simple, missile, or melee] Any creature that physically interacts with a visual illusion will gain an automatic Disbelief save. If attempting to interact with an actively controlled illusory creature, this is treated as a missile or melee attack (the type of attack is chosen by the attacker, including a contact attack). Illusory creatures not actively controlled can be automatically hit/interacted with. Only one interaction save per creature per illusion spell is permitted (even if multiple interactions occur).

• Disbelieve Activity. [complex] Any creature that performs a complex activity to disbelieve can make a Disbelief save as long as they indicate what they are disbelieving.

ADJUSTMENTS TO DISBELIEF SAVING THROWS

Ally Indicates Something is an Illusion. This grants an immediate saving throw at +4 to the attempt. The ally must have successfully made a disbelief save versus the illusion. This immediate save is granted only once per illusion.

Keen Senses. Creatures with keen senses allowing a sense invisible check (not due to hit dice) gain a +4 bonus to disbelief saves due to interacting with illusions.

Missing Component. A missing component to an illusion, such as smell, sound, or heat will grant a +2 to +8 to disbelief saves depending upon circumstances (per the GM).

Proof. An ally that "proves" the existence of an illusion (walking through an illusory wall, etc.), allows for automatic disbelief (no save required) by performing a disbelieve activity.

Spell Caster Knowledge. A spell caster creating an illusion of subject matter unfamiliar to themselves will grant a +1 to +4 bonus to disbelief saves (per the GM). e.g. Studied but never seen (+4) to experienced personally under 4 times (+1).

FAILED SAVES

A creature is allowed only one interaction save versus an illusion and one immediate save due to an ally indicating it is an illusion (but not displaying proof). Thereafter, a creature can disbelieve as a complex activity each round until the save is made or the illusion is proven to be an illusion. The GM will adjudicate the circumstances of proof, but any illusions actively maintained by the spell caster can be altered so that proof is difficult.

MINDLESS CREATURES

Mindless creatures cannot disbelieve illusions unless they interact with them. However, those mindless creatures without traditional sight organs will ignore phantasmal illusion spells or hallucinatory illusion spells. 

SENSE INVISIBILITY CHECKS AND ILLUSIONS

Sense Invisibility. If a creature has the ability to sense invisible due to keen senses (not hit dice), this check will also allow the creature to ignore the illusion when within 30 feet (roll this check before any saving throws due to interacting with an illusion).

INFRAVISION

An illusionist using an illusion spell other than a phantasm can fool infravision. However, an illusionist that has never experienced infravision themselves grants a +2 on disbelief saves if part of their illusion ends up in darkness.

SPECIAL SENSES

Certain creatures will have special senses that allow automatic detection of illusions (typically leading the creature to ignore them). Examples are ooze senses and echolocation.

MAGIC RESISTANCE

Creatures with magic resistance will only be allowed their magic resistance check if physically contacting the illusion in melee range with a touch (contact) or melee attack. If the magic resistance check is successful, the creature is considered to have disbelieved the illusion. If the check fails, saving throws for interaction disbelief are made normally. No other magic resistance check will be effective against that illusion going forward.

LIKELIHOOD TO DISBELIEVE

Players will control attempts to disbelieve for any creature or character controlled by them. For creatures under the control of the GM, use the following procedure to determine disbelief as an activity.

First determine the likelihood of belief—That is, the illusion represents something that is:

1. Highly Unlikely (multiplier 10). These illusions make little sense to the viewer and the most probable explanation is that it is an illusion. e.g. Appearing pits, walls appearing from thin air, unfamiliar monsters appearing, etc. Ironically, some of these effects will be considered "strange and unexpected" by more experienced (higher Intelligence and hit dice) creatures due to their experience with magic.

2. Strange and Unexpected (multiplier 5). Unexplained effects like immolation, rushing water, obstructions where there were none previously, or duplicating high level spell effects. Familiar creatures acting strangely, etc. The illusion might have an explanation (for not being an illusion), but it may be far fetched.

3. Realistic or Expected (multiplier 2). These illusions are expected and/or realistic. i.e. A bridge where one has always been, but the illusion covers the fact that several planks are missing. In some cases, the GM may determine the multiplier is 0 until the illusion is interacted with.

Important Note. Creatures will not always immediately use an activity to disbelieve, they will rank order the activity based on the risk of performing it to the exclusion of other activities. Of course, interacting with an illusion grants an immediate save in any case.

Base Chance to Disbelieve: 0% + Intelligence Score (for Low Intelligence or higher) * multiplier. 

A check rolled equal to this score or lower indicates the creature will attempt to disbelieve.

Creatures with keen senses will always gain their sense invisibility check to automatically detect an illusion when within 30 feet (see above).

ADJUSTMENTS TO DISBELIEVE CHECKS

High Intelligence or Wisdom. Creatures with a 15+ Intelligence or Wisdom will have a +10% greater likelihood to disbelieve an illusion (for each). Illusionists double this adjustment.

Missing Component. A missing component to an illusion, such as smell, sound, or heat will automatically drop one rank (i.e. Unexpected to Unlikely). If a creature has the ability to sense invisible due to keen senses, this is also added to the likelihood to disbelieve.

Unrealistic Circumstances. Creatures wearing plate mail without being delayed, moving faster than normal, etc. will automatically drop an illusion one rank.

Companion Indicates an Illusion. If an ally indicates the effect is an illusion, the disbelief likelihood is 100% (to attempt the save). The ally must have successfully made a disbelief save versus the illusion.

EFFECTS OF ILLUSIONS 

Number of Active Creatures. The number of active creatures is limited by caster level. "Active" means interacting with real opponents or NPCs. Up to 1 Man-sized, 2 Small, or 0.5 Large creatures can be active per caster level.

Thus, a 7th level caster can use a spectral force illusion to create a group of 15 orcs, but only 7 orcs can attack or defend themselves. Attacks on the inactive orcs will automatically hit. The inactive orcs will appear to be acting normally (ie. in a defensive stance, looking around at enemies, etc.), but will not otherwise take actions or react to stimuli. Note: The caster cannot interchange active and inactive creatures. Once a set of active creatures has been created, these will be the only illusory creatures active for the spell or effect.

Armor Class. The best AC afforded to active illusory creatures is 10 minus 1 per caster level, modified by the spell caster's Intelligence: 16-17: +2; 18-19: +3; 20+: +4. Creatures will otherwise have their expected AC even if this is worse than the best AC possible. For example, a brown bear will have an AC of 6 no matter the level of the spell caster. If an illusory creature is wearing armor, armor defense will (appear to) work normally.

Damage. [mind-affecting] Any damage done by the spell is considered a mind-affecting effect. While illusory damage appears to be normal damage, creatures will not become unconscious due to illusory damage. That said, illusions can do real, if limited, damage to those that believe the effects. Thus, an illusory orc wielding a hand axe will appear to strike for normal damage but actual damage will be limited. A creature believing the effect might still lose morale due to illusory damage. 

Maximum Illusory Damage. In any case, no matter the effect or spell type, illusory damage is limited to 1d6 per caster level per round (or less). Assuming creatures miss their saving throw, this translates into 1d2 real damage per die—however, a spell caster is limited in the amount of real damage they can do (based on spell type). 

Maximum Real Damage. Phantasm effects are limited to a maximum of 2 points of damage per caster level, total. Spectral effects are limited to a maximum of 2 points of damage per caster level per creature. Once the limit is reached, no further real damage can be dealt by the spell. When dealing with illusory creature missile or melee attacks, only one die of damage is allowed per strike (1d2 per attack). If an area of effect attack is made (fireball, dragon breath), real damage will be up to 1d2 per caster level per creature (phantasms don't create thermal effects).

Illusory Creatures, Actions, and Magic Items. Illusory creatures that clearly break game rules will allow immediate automatic disbelief (without requiring a roll), even if edge cases (items and spells) might explain their actions. Thus, it's usually a bad idea to attempt to convince opponents that the human they are facing is hasted with a crossbow of speed, an active flying spell, and wielding a flame blade. Obviously, the GM must make the call, but without the proper set up or activity, the illusion will likely fail against opponents with a Low or better Intelligence rating. 

Example #1. A 1st level illusionist (Int 17) facing 3 goblins casts phantasmal force, creating an illusion of 5 orcs in the area of effect (which is in daylight). One orc is active and moves to attack using hand axes. Orcs are known to be nearby, the caster spoke commands in orcish during declaration, the caster made a successful legerdemain check, and the goblins hate the orcs. The GM determines the illusory orcs are Expected, but the moving orc makes no noise and drops this to Strange. These goblins are not the smartest in the tribe and have a 35% chance to disbelieve. They fail the check and believe they are being faced by 5 orcs. The goblins attack three different orcs with slings (as they are not smart enough to concentrate fire). The active orc has an AC 7 and the others can be hit automatically. The 1st goblin misses and the others automatically hit. Their stones pass through the orcs and they automatically make their saves. The 1st goblin gains an immediate disbelief save as it's allies squawk, but, even with the bonus, the save is missed. The illusory active orc enters melee. The goblins (somehow) succeed their morale check at the end of the round. The next round, the illusionist wins initiative and the illusory orc strikes the goblin that failed it's save. The goblin gains another save having interacted with the illusion (the GM determines this is at +6). The goblin misses it save and takes 1d6 illusory damage (1d2 real damage). The illusory damage rolled would normally cause the goblin to become unconscious but it appears the goblin escaped with 1 hit point (real damage was only 1 hit point). The other two goblins see the illusionist (who is concentrating) wave his hands ominously (as a ruse) and see their ally get hit for what appears to be real damage. On their group initiative, the goblins flee, with the illusory orc taking an ineffective free attack to send them along their way. The illusionist can then have the active illusory orc pursue to the limit of the area of effect. The other orcs cannot be caused to move.