With a touch, you place an illusion on a willing creature or an object that isn’t being worn or carried. A creature gains the Mask effect below, and an object gains the False Aura effect below. The effect lasts for the duration. If you cast the spell on the same target every day for 30 days, the illusion lasts until dispelled.
Mask (Creature). Choose a creature type other than the target’s actual type. Spells and other magical effects treat the target as if it were a creature of the chosen type.
False Aura (Object). You change the way the target appears to spells and magical effects that detect magical auras, such as Detect Magic. You can make a nonmagical object appear magical, make a magic item appear nonmagical, or change the object’s aura so that it appears to belong to a school of magic you choose.
* - (a small square of silk)
I TOLD YOU ALL IT WORKED LIKE THIS!! IT DOES EFFECTIVELY CHANGE THE CREATURE TYPE!! 5.5E FOR THE WIN! CHANGING CREATURE TYPES WITH THIS IS RAI!!
So my Hold Person spell will work on a Beholder? Neat....
willing creature
Technically you could enchant a creature into being willing then changing it into a humanoid and possess it with magic jar.
So, for a 2nd level spell, meant to *mask* a creature type, you're turning a creature into another creature type, allowing Hold Person to work on Dragons/Beholders/Owlbears/Mimics/Animals/Golems/Celestials/Fiends, turn a Dragon into a Fiend for Smiting purposes, and turn anything into a specified creature type for Antipathy, Hallow, Glyph of Warding, Guards and Wards, Forbidance, or any other spell that works on specified creature types?
And this is an illusion spell of 2nd level.
/design/fail.
If someone were to cast this on a magical item to make it appear non-magical, would Detect Magic still sense the illusory magic from Nystul's Magic Aura around the item?
That is a real possibility, but the creature this is cast on needs to be a willing creature. Though, I'm sure there are ways to coerce them to be willing, such as Suggestion.
When you cast this on a non-humanoid creature and choose humanoid for the creature type, will you be able to cast Animate Dead on the corpse because it’s considered humanoid to spells and magical effect?
Right. And using a charm spell to make them willing, magic aura to make them able, then a hold person spell to make it work on a beholder (or powerful monster of choice)- well… that’s a fair trade vs a single level 4 (or whatever level) hold monster.
Willing Target!!
That seems like more steps than it's worth, I think the real power of this spell is in changing yourself to a creature type that can't be effected by a lot of spells. In a good DMs hands this spell can get crazy, they could have the evil wizard make fake magic items to chase, while you're busy with that they can be turning the undead army they have into celestials so your cleric can't turn them.
Technically technically: An enchanted creature isn't willing. Their will stays the same, its only being overridden by your will. If it's not their will, they're not willing.
Suggestion might actually work, but that still requires the target to think that your suggestion is rational (rules-lawyers: yeah, I know about the change -- but the DM gets the final say, and very few DMs would rule it that way). Personally, I'd rule that Charmed creatures' wills are overridden; and so exploiting that to apply magical effects equals an automatic failure. Buuut, if you successfully influence a charmed creature and then unenchant them, you're good to follow through if they're still on board with your idea.
they really should have clarified the wording with this spell a lot.
Clearly the intent here is to have the creature act as the other creature type for the purposes of detect evil and good, spells with triggers like sequester, alarm and glyph of warding, and possibly even hallow, with it not being supposed to change the creature type for the purpose of being a legal target of stuff like polymorph, magic jar, hold person etc.
Perhaps the designers simply hoped that the room for abuse would be minimal when the spell can only target willing? Who even knows
This is the correct answer IMO.
Nystul's Magic Aura is a spell from the Illusion school. It is masking your creature type with a glamour, not physically changing your creature type. Nystul's could definitely make it so spells or abilities to detect undead will not work on the vampire mage NPC who has this cast on himself because the illusion fools the detection magic. But, Illusion spells do not fundamentally alter you in any way. Because of this, you cannot use Nystul's to somehow trick the Magic Jar spell into working on a creature that isn't a Humanoid just because you placed an illusion on them.
Now, if Nystul's was a spell from the Transmutation school then I'd be more inclined to agree that it could allow shenanigans like this. In that case, it would physically alter your body like how Alter Self physically changes you. But, Nystul's is not a Transmutation spell and because of that a DM could correctly say "No, you cannot use this spell to cast Hold Person on the dragon. Nice idea though!"
With that said, this spell is narratively very useful for the DM to foil detection abilities and spells the party may employ or it could be very useful for the party to cast onto the Rogue before they try to sneak into an undead filled dungeon to scout around.