"The Legend of Korra" Book 4 will release this coming week, and the full-length trailer has caught everyone's attention.

In the full-length "Legend of Korra" trailer, we know that Book 4 will take place three years after the events of Book 3, although other details are still unknown.

The trail also heavily features a relatively new character first introduced toward the end of "The Legend of Korra" Book 3 named Kuvira. Based on the trailer, many fans theorize that Kuvira could be a villainous character in Book 4.

"We don't have any kind of confirmation on what Kuvira's backstory is, other than what Suyin has told us, but there are a lot of really cool theories," said Emergency Awesome.

One popular theory is that Kuvira is the love child between Zaheer and Suyin, based on a photo shown in a "Legend of Korra" Book 3 episode.

"It all stems from this picture that was in Suyin's office of her and her circus troupe," added Emergency Awesome. "It just looks like this person is Zaheer, so it's possible they had some kind of relationship, and Kuvira was the result of that."

But perhaps the most exciting portion of the trailer comes at the very end of the trailer, where Korra utters, "I can't believe it."

"Toph?"

"I was already emotional by the time the ending frames rolled by but then they threw the Toph bit and I screamed," commented Patch-Eye on Hypable.