As a touch spell, this can be cast through a familiar...  Must get DM's approval for a chicken familiar!  ;-) 

PC:  "I write the message by casting Illusory Script through Henrietta."
DM:  "What does the writing look like for other people?"
PC:  "You have to ask? Literal chicken scratches!"

Ha! Nice

I think there should be an option to cast it at 2nd level to have it last until dispelled, just like Magic Mouth.
As a DM, I want one of my NPCs to use it to keep records of his narious deeds, that the PCs now have a chance of uncovering.

So.... I know the intent seems to be to encode / hide messages, but could this be used to forge documents? It specifies that you can make your message appear to be any other message. Like a deed to a plot of land or an official summons from a duke? Interesting that there is no DC check to discern the true meaning.

Can someone please expand on ''To you and any creature you designate when you cast this spell...'' in terms of limitations?

Does the designated creature need to be nearby when the spell is cast?

If yes, as this spell can be cast by proxy (familiar) do the creatures near the familiar count?

If no, can I use a broad generalisation such as alignment or a specific requirement such as being a member of an organisation I wish to send a message to?

trick people into signing away their souls with a contract that they can only read a false illusory version of!!!
MWAHAHAHAHAH

Quote from Jety_Lefr >>

trick people into signing away their souls with a contract that they can only read a false illusory version of!!!
MWAHAHAHAHAH

Not to be a "hum actually" person, but magical contract cannot be agreed to by mistake. The deal making only occurs if the person is actively and knowingly agreing to the terms of the contract. You cannot sell away your soul unknowingly.

Quote from mouarflenoob >>

Quote from Jety_Lefr >>

trick people into signing away their souls with a contract that they can only read a false illusory version of!!!
MWAHAHAHAHAH

Not to be a "hum actually" person, but magical contract cannot be agreed to by mistake. The deal making only occurs if the person is actively and knowingly agreing to the terms of the contract. You cannot sell away your soul unknowingly.

 ► First of all, I don't believe there's anything in any of the source books that suggest such a rule. It'd be up to the Dungeon Master to decide if that sort of rule takes place in their world (and in the games I run, it's fair game).
► Secondly, there's no reason the contract itself has to be magical. Any unscrupulous devil, fey, or celestial can simply make the claim that they are in their rights to take someone's soul with their own power, citing the contract as the authority which grants them the right.

It's like fine print, that anyone with truesight can read. I you don't look closely enough (or can't, hehehe), it's your own fault as far as evil NPC/PC is concerned.

Anyone else feel like this could be an Artificer spell? It's magically pushing a common thing (writing), and figuring out how to make illusions with lead ink feels like a magic nerd's domain.

Quote from mouarflenoob >>

Quote from Jety_Lefr >>

trick people into signing away their souls with a contract that they can only read a false illusory version of!!!
MWAHAHAHAHAH

Not to be a "hum actually" person, but magical contract cannot be agreed to by mistake. The deal making only occurs if the person is actively and knowingly agreing to the terms of the contract. You cannot sell away your soul unknowingly.

I am inclined to agree with you.

However, devils using invisible (to mortals) ink is a longstanding trope in D&D, so I fear precedence may be against us.

The best part of this spell is that when it ends the original message also disappears.

Note to self: Great discussion of the spell's roleplay uses here: https://wizardofthetavern.com/best-wizard-spells-5e/ 

Not just for forgeries! 

• You can stick a note to someone's back that only a few people can see.
• You can use it around religious types -- when they realize they're the only one who can see it, maybe it's a message from their god!
• You can make graffiti on a wall that looks like 'up with the king' to the cops, and 'down with the king' to the peasants. All sorts of mischief.

Quote from Crogonint >>

I'm just trying to figure out how you get a single use portion of LEAD paint worth 10 GOLD. World's worst transmutation spell? :D

 Sire, thy reverse alchemy doth make me laugh. :D

Quote from Jety_Lefr >>

trick people into signing away their souls with a contract that they can only read a false illusory version of!!!
MWAHAHAHAHAH

 Yes!

You could also use this for (chaotic) good: trick them into signing contracts for charitable giving or community service. 

Also: Illusory Script + Charm Person/Friends + Disguise Self = so much mischief at Level 1! 

"MENE, MENE, TEKEL, UPHARSIN"

Illusory Script is a spell you can get a lot of mileage out of as an illusionist, especially combined with Malleable Illusions. One moment, that piece of paper in your hands is an in official invitation to the ball written in the host's own hand. The next, that same paper says you have a warrant for the arrest of the Countess on the authority of the crown. Not sure what exactly you need for the situation? A quick Detect Thoughts can let you know exactly what that castle guard is expecting to see and then you can make it so. Endless uses for someone inclined towards espionage!

Psychic Paper, anyone?

Ultimate low-cost spell to girlboss gaslight gatekeep. Especially gaslight.