[RPG] When should I have an NPC actively investigate an illusion created by the Phantasmal Force spell


The phantasmal force spell can be broken if the victim examines the illusion and makes a successful investigation check against the spell's DC.

What general guidelines should I use to decide when the victim of phantasmal force should use its action to examine the illusion?

Suppose the caster makes an orc think it is being attacked by a wolf.

Should the orc always examine the wolf until the spell ends? Or should the orc use its action to attack the wolf, defend itself, or run away?

Best Answer

Depends on the situation.

There are two things to consider.

The target rationalizes any illogical outcomes from interacting with the phantasm. For example. a target attempting to walk across a phantasmal bridge that spans a chasm falls once it steps onto the bridge.


The target can use its action to examine the phantasm with an Intelligence (Investigation) check against your spell save DC

Given that the targeted creature failed the first save**, no matter how smart a creature is, if it rationalize any illogical outcome it would not use any action to investigate the illusion. This hold true for any direct interaction between the illusion and the target.

But, if there is a situation where the affected creature has a reason to believe it might be an illusion, it can use its action as the rule states. For example, an ally seeing him fighting with a ghost might help him yelling "it is an illusion" or "it is in your head". In this case, the creature has a reason to suspect is an illusion an use its action accordingly.

** The description of phantasmal force says:

The target must make an Intelligence saving throw. On a failed save, you create a phantasmal object, creature or other visible phenomenon of your choice that is no larger than a 10-foot cube and that is perceivable only to the target for the duration. This spell has no effect on undead or constructs