I've seen much debate on how different DMs treatment of illusions can cause their power levels to vary wildly from game to game. It just occurred to me that there is already a precedent for automatically determining whether a creature sees through an illusion, in addition to the "use an action to check" clause.
Note: I haven't read through the DMG but I haven't seen this mentioned before so correct me if this is redundant.
Passive Investigation is mentioned in the PHB under the Observant feat (pg 168). The intention seems to be that any creature with a passive investigation score above an illusion's spell DC should automatically see through the illusion. If no one sees through it passively, THEN the DM discretion comes in as to whether the creature should make an active investigation roll. Now here there is some room for leeway, but it makes sense for the DM to use some sort of familiarity level to determine whether the illusion should be checked, as well as considering if the creature saw the illusion come into existence
I.E. Very Familiar or Saw Illusion Materialize - Automatically check (maybe advantage if it saw it come into form)
Somewhat Familiar - 75% chance to check
Seen Once or Twice - 50% to check
Never seen - 25% chance to check
For example - a gnome illusionist is hiding in an illusion crate in an Orc storeroom. An orc patrolman walks through on his daily rounds. The orc's passive perception and passive investigation are low enough so that he doesn't hear the gnome and doesn't detect strange features with the crate, however he is very familiar with this storeroom and hasn't seen this crate here before. He makes an investigation check (brief stare studying the crate) and rolls high enough to determine that something is wrong. THEN he goes and tries to interact with the crate and discovers that it is an illusion and the gnome is busted.
DMs - what do you think? Do you already use Passive Investigation? Would Passive Investigation create a more solid baseline for the power of illusions? Is this a stupid statement that everybody already knows about? Let me know
Note: I haven't read through the DMG but I haven't seen this mentioned before so correct me if this is redundant.
Passive Investigation is mentioned in the PHB under the Observant feat (pg 168). The intention seems to be that any creature with a passive investigation score above an illusion's spell DC should automatically see through the illusion. If no one sees through it passively, THEN the DM discretion comes in as to whether the creature should make an active investigation roll. Now here there is some room for leeway, but it makes sense for the DM to use some sort of familiarity level to determine whether the illusion should be checked, as well as considering if the creature saw the illusion come into existence
I.E. Very Familiar or Saw Illusion Materialize - Automatically check (maybe advantage if it saw it come into form)
Somewhat Familiar - 75% chance to check
Seen Once or Twice - 50% to check
Never seen - 25% chance to check
For example - a gnome illusionist is hiding in an illusion crate in an Orc storeroom. An orc patrolman walks through on his daily rounds. The orc's passive perception and passive investigation are low enough so that he doesn't hear the gnome and doesn't detect strange features with the crate, however he is very familiar with this storeroom and hasn't seen this crate here before. He makes an investigation check (brief stare studying the crate) and rolls high enough to determine that something is wrong. THEN he goes and tries to interact with the crate and discovers that it is an illusion and the gnome is busted.
DMs - what do you think? Do you already use Passive Investigation? Would Passive Investigation create a more solid baseline for the power of illusions? Is this a stupid statement that everybody already knows about? Let me know