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Thief detect illusion doesn't detect some invisibility

reko35reko35 Member Posts: 17
I raise 'detect illusion' over 100 but it's often useless against some invisible enemies while true sight works. Taking Ketta, who is one of the celestial fury group, as example, her second invisibility can be dispelled but the first cannot. I don't know which is by potion or ring. Anyone knows the reason?
I don't find items with nondetection effect. But she's got a 'minhp1', which doesn't work as its name suggests since she can be killed.

Comments

  • jmerryjmerry Member Posts: 3,846
    Ketta starts out invisible from a non-droppable ring, which grants non-illusionary invisbility to simulate him using his thief abilities to hide. A thief's Detect Illusion ability doesn't help against that, and shouldn't.
    Once he's revealed the first time, he starts using his stack of potions of invisibility. The effects of those potions do count as illusions, so the thief ability is effective against them.

    The "minhp1" item is there to ensure you can't kill him before meeting him properly upstairs. It's removed by script as soon as you enter the area you're meant to actually fight the group in.

    Why does True Sight (and Oracle) work where DI doesn't? Because those spells, in addition to removing illusionary protections, also directly remove invisibility. And that part doesn't care where the invisibility came from.

    The "nondetection" effect is actually rather narrowly defined; it only protects against the "detect invisibility" effect. Effects that strip your illusionary protections go through it just fine, and the Nondetection spell is itself classified as an illusionary protection so it doesn't help against Oracle and True Sight at all.
  • reko35reko35 Member Posts: 17
    jmerry wrote: »
    Ketta starts out invisible from a non-droppable ring, which grants non-illusionary invisbility to simulate him using his thief abilities to hide. A thief's Detect Illusion ability doesn't help against that, and shouldn't.
    Once he's revealed the first time, he starts using his stack of potions of invisibility. The effects of those potions do count as illusions, so the thief ability is effective against them.

    The "minhp1" item is there to ensure you can't kill him before meeting him properly upstairs. It's removed by script as soon as you enter the area you're meant to actually fight the group in.

    Why does True Sight (and Oracle) work where DI doesn't? Because those spells, in addition to removing illusionary protections, also directly remove invisibility. And that part doesn't care where the invisibility came from.

    The "nondetection" effect is actually rather narrowly defined; it only protects against the "detect invisibility" effect. Effects that strip your illusionary protections go through it just fine, and the Nondetection spell is itself classified as an illusionary protection so it doesn't help against Oracle and True Sight at all.

    Thank you for the very detailed explanation!
    Can 'detect illusion' discover a thief hiding at the beginning without using the potion? I remember many fail-to-detect cases before Ketta but I thought it was because of insufficient DI points or undroppable nondetection cloaks.
  • jmerryjmerry Member Posts: 3,846
    A thief's hiding ability isn't an illusion, so no. You can't detect a thief hidden that way with thief Detect Illusion. Or the Detect Illusion spell, for that matter.

    The AI doesn't normally use thief abilities like that, so instead it simulates them with invisibility effects or undroppable items. Which also aren't illusions.

    What can you use against that initial invisibility? You can use spells with the "detect invisibility" effect, such as Detect Invisibility (arcane level 2), Invisibility Purge (divine level 3), Oracle (arcane level 5), True Seeing (divine level 5), and True Sight (arcane level 6).
    What does non-detection do? It blocks that "detect invisibility" effect, and that's all it does. Unfortunately, the spell version counts as an illusionary protection so Oracle and True Sight/True Seeing remove it. And they have their "detect invisibility" effects last, so the same spell that removed the non-detection also breaks the invisibility to reveal the creature. This makes the item version (usually a cloak) vastly better than the spell.
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