1st-level Spell: Secret Missive

Aspetheurgy (Illusion)

You pen a secret message on a parchment, paper, or other writing material. When you write the message, choose a password or passphrase; when a creature speaks this code while holding the parchment, the secret message appears for 10 minutes before fading again. Alternatively, you can specify a creature. The message automatically appears when it holds the parchment. You can write any other text on the parchment, which becomes invisible anytime the secret message is displayed. When the spell ends, the secret message disappears forever.
Creatures with truesight can see the secret message. A Dispel Magic cast on the parchment ends the spell without revealing the secret message.
The spell's duration is related to the quality of ink used. Magical ink worth 10gp gives it a duration of 10 days. More expensive ink lasts an additional day for each 1gp spent; if 100gp worth of magical ink is used, the duration becomes permanent.
Source: SDS (Illusory Script)

• Casting Time: 1 minute
• Range: Touch
• Components: S, M (supernatural ink worth at least 10gp, which the spell consumes)
• Duration: Special
• Ritual: Yes