Programmed Illusion

You create the illusion of an object, creature, or some other visible phenomenon within range of the spell that activates when specific conditions occur. The illusory effect is undetectable until then. The illusion can’t be larger than a 30-foot cube, and during casting you decide how the illusion behaves and what sound it makes. The imagined performance can last up to 5 minutes.

When the specified conditions occur, the illusion activates, appearing and acting as you described. Once it finishes performing the act, it disappears and remains dormant for 10 minutes. After that time, the illusion can be reactivated.

The activation condition can be as generic or as detailed as you choose, though it must be based on visual or auditory conditions that occur within 30 feet of the area. For example, you could create an illusion of yourself appearing to warn others attempting to open a trapped door, or you could program the illusion to activate only when a creature says the correct word or phrase.

Physical interaction with the image reveals that it’s an illusion, since objects can pass through it. If a creature uses an action to examine the image, it can determine that it’s an illusion with a successful Investigation check against the DC to avoid your spell. If a creature discerns the illusion for what it is, the image becomes transparent, allowing it to be seen through, and any sound the illusion makes becomes muffled to that creature.