You try to have full access of a creature’s mind and make it see whatever you want. The targeted creature must succeed on a wisdom saving throw or be affected for the duration. If the creature is affected by this spell, the caster get to chose what the creature see, but it can only be one distinct thing at a time. Here are some examples.
Complete darkness. The affected creature can perceive nothing but darkness and cannot see anything even if it is right in front of it, if it as truesight, darkvison, etc. If the affected creature want to move, it as to move in a random direction. If the creature want to attack, it have to target a random location. Since the creature can’t see, it automatically fail any ability check that requires sight. Attack rolls against the creature have Advantage, and the creature attack rolls have Disadvantage. The creature is also have the deafened condition and doesn’t feel any sensation while being touched or touching something.
Invisible world. For the affected creature, any number of creatures or objects chosen by the caster appears invisible and cannot be seen by the spell see invisibility or other features that allow to see invisible creatures. The creatures and objects that appears invisible for the affected creature make no sound, and if it touches one of them, the creature senses that something is blocking its path, but it remains invisible. Attack rolls against the creature have Advantage, and the creature attack rolls have Disadvantage for the creatures that appears invisible.
Fake appearances. For the affected creature, any number of creatures or objects chosen by the caster appears in a new form as if with the spell disguise self with no size limitations. Any contact that the affected creature make with any creatures or objects with a new form doesn’t reveal that it is an illusion and the creatures with a new form make no sound for the affected creature. If a creature take a new form and the affected creature sees the transformation, it still think that the creature with a new form is what it as transformed into.
Great apparition. You make appear to the affected creature an illusion as if with a spell like silent image or major image, but without any limitations on size. The illusion seems real, including sounds, smells, and temperature appropriate to the thing depicted. It can cause conditions to the affected creature if it seems appropriate to the DM, for example : a terrifying illusion could cause the frightened condition.The illusion can move and do anything you can imagine, besides interacting with others objects or deal damage. Physicals interactions with the image doesn’t reveal it to be an illusion, the affected creatures still pass through, but think it is doing so by magic.
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