She-Ra: Princess of Power (1985)

S1E17 A Loss for Words

After Hordak and Shadow Weaver learn that She-Ra plans to publicly endorse the Great Rebellion, they devise a sinister scheme to silence her permanently. By stealing her voice, they hope to cripple her influence and leave the Rebellion without its most powerful advocate. As She-Ra struggles to communicate without her voice, Adora must find a way to outsmart her captors and reclaim what was taken from her before the Rebellion's morale is shattered.