Mordenkainen's Lost Notebook

Bothersome Babble

2-level Enchantment

Choose a target within range who can see and hear you. That creature must succeed on a Wisdom saving throw or find itself unable to be understood through verbal communication. No matter how hard it tries, it can’t speak a language, but only utters nonsense sounds. Its ability to write is unaffected. To cast a spell with a verbal component, the subject must succeed on a Concentration check, the DC of which equals your spell save DC + the level of the spell to be cast.