Editing Homebrew Spells (section)

=== Cloud of Stupid Gas ===
''9th-level evocation''

Casting Time: 1 action

Range: Any point you can see within 60 feet

Components: S

Duration: Concentration, up to 30 minutes

You concentrate on a point you can see out to 60 feet and spawn a cloud of colorless, odorless, invisible gas. All creatures that enter the range or are inside of it already with an Intelligence ability score of 2 or higher to must make a Wisdom saving throw.

On a failure, the creature’s Intelligence and Wisdom ability scores are reduced to 1. An affected creature cannot cast spells, activate magic items, understand language, or communicate in any intelligible way. The creature can, however, identify its friends, follow them, and even protect them. 

At the end of every 30 days, the creature can repeat its saving throw against this spell. If it succeeds on its saving throw, the spell ends. The spell can also be ended by Greater Restoration, Heal, or Wish.