At the end of the first season of Star Wars Rebels
Tarkin takes Kanan to Mustafar to extract information.
When asked about the planet, Hera says
I've only heard that name once, from Kanan. He said Mustafar is where Jedi go to die.
Is there anything else in the current Disney canon to corroborate this?
Kanan wouldn't have known about the duel between Obi Wan and Vader so he wouldn't be referring to that.
Is this referring to something yet to be revealed?