- "A ghastly light will fill the swale."
"The swale? What's a swale?" - ―Darth Vader and Darth Sidious
The swale was tied to the Legend of the Sith Witch. According to Darth Vader, a ghastly light filling the swale was a sign that the Sith Witch of Mustafar was going to arrive.[1]
Appearances
LEGO STAR WARS: Celebrate the Season — "The Sith Witch of Mustafar" (First mentioned)