You speak a word of power that intercepts the thoughts of one creature you can see within range making fine motor control impossible. If the target has 100 hit points or fewer, it can't speak anything other than gibberish and can't perform any feat that requires fine motor control such as lockpicking or performing somatic components.
Otherwise, the target can't speak until the end of its turn.
The target must make a Constitution saving throw at the end of each of its turns. On a successful save, this effect ends.