Illusion magic

ILLUSION MAGIC

I have struggled with how illusionist magic operates. I had an illusionist is a previous campaign, but they didn't test the boundaries of the magic system.

I have another illusionist in my current campaign and decided that I needed to put pen to paper, especially as they may be acquiring a nearly fully charged wand of illusions!

Incidentally, both of these illusionists were NPCs who were taken over by players after their characters died. The first was Grastic Hammerclay. The second was a gnome from my Absorbing Eye adventure.

This explanation will probably make it into my ADVANCER Rules.

Illusion vs. phantasm

All forms of illusion magic includes a sensory aspect, called an illusion, and a mental element, called a phantasm. The phantasm affects every intelligent creature who senses the illusion. At a minimum, the phantasm makes the illusion seem real, fleshing it out and filling in gaps. More powerful phantasms can cause damage, physical effects such as blindness, deafness or paralysis, or even death. A phantasm is a form of mental attack. 

Once the illusion is sensed, the phantasm cannot be avoided simply by closing off one’s senses. However, the phantasm will not affect those who are immune to mental attacks, such as undead and unintelligent creatures.

“Seeing through” and disbelieving an illusion

“Seeing through” an illusion allows one to perceive both the illusion and the reality. If an illusion has been seen through by a creature, the phantasm will have no affect on the creature. 

“Disbelieving” is the act of the mind resisting the phantasm. It is one way to “see through” an illusion. “Disbelieving” requires a saving throw vs. spells (adding any WIS bonus for mental attacks). A saving throw is not given immediately upon sensing the illusion. The GM will allow a saving throw when allowed by the spell description. However, not all illusion spells permit a saving throw. 

Generally, where a saving throw is permitted by the spell, it will be allowed when the creature begins to doubt the reality of the illusion or when the phantasm will have a physical effect on the victim. If the saving throw is failed, it may be repeated if circumstances change, eg, a compatriot “sees through” the illusion and communicates this. 

Another way to “see through” is to use a magic item, such as a gem of seeing, or a spell, such as detect illusion (Illusionist 1), true seeing (Cleric 5) or true sight (Illusionist 6). Magic resistance may also allow a creature to “see through” an illusion.

Dispelling an illusion spell 

Dispelling an illusion spell means the illusion and phantasm disappear completely. Damage or death caused by the phantasm are not reversed, but any effect requiring the ongoing action of the phantasm, such as blindness or paralysis, will end. “Seeing through” an illusion does not dispel it. 

Dispelling can be accomplished by magic, such dispel magic or dispel illusion. However, many illusion spells can also be dispelled by touching the illusion. The nature of the touch differs by illusion spell but typically includes touch by an intelligent creature or striking or killing an illusory monster. 

To explain this unique weakness of illusion spells, we might theorize that it is related to the fact that an illusion spell is maintained, either by the illusionist, who does so through concentration, or by a program, which has been put in place by the illusionist. The illusionist or program can be overcome, such as when an illusion is touched, an illusory monster is killed, or an illusory monster is struck and does not react plausibly. If overcome, the spell will fail completely. 

Limitations on phantasmal force

Most illusion spells have a limitation as to what types of illusion or phantasm they can produce. Although more open-ended, the phantasmal force family of spells do have certain limitations. 

Phantasmal force was originally devised to create an illusion of combat forces, which attacked and did damage through a phantasm, such as phantasmal missiles. While phantasmal force can create a great variety of illusions, the effects of its phantasms are tied to the original use of the spell. For instance, phantasmal force can cause damage, which can lead to death, but it cannot replicate the effects of magical attacks. Situationally, it may cause paralysis. Also, damage caused by illusions other than combat forces will tend to be less believable and will grant a bonus to saves to “disbelieve”.

Other illusion spells have other mental effects (eg, blindness, deafness, fear, phantasmal killer), and shadow magic allows the replication of four specific mage spells: cone of cold, fireball, lightning bolt, and magic missile.