The Legend of Korra, Season 2

[Cut back to Jinora, Tenzin, Kya, and Bumi in the Spirit World]

Jinora:
The world is in trouble.

Tenzin:
What are you talking about? How do you know?

Jinora:
I can feel it.

Bumi:
What happened?

Jinora:
It's Korra. [Jinora hands her father a butterfly spirit] This light spirit will guide you out of the Spirit World. [She begins to fade away] I have to go help.

Tenzin:
Jinora, wait! [she vanishes]

[Back in the physical world, Unalaq and Vaatu grow to enormous size, shocking Korra, Mako, Bolin, and Desna and Eska, who look on in horror. Unalaq and Vaatu, now known as Unavaatu, speak in unison]

Unavaatu:
Now, ten thousand years of darkness begins!

[Using the spirit lights, Unavaatu teleports away, sending out a shockwave that knocks out everyone present]