Nintendo pamphlet confirms Link and Zelda are "deep within the caverns beneath Hyrule Castle" in Zelda: Breath of the Wild 2 (UPDATE)

UPDATE - Unfortunately, this isn't new and doesn't come from Nintendo. This was originally from GamesRadar in 2019. You can find the original post below.

We've only had one teaser video for The Legend of Zelda: Breath of the Wild 2 so far, but that's been enough to fuel speculation on the game ever since. Fans are looking to glean any tidbit of info possible, and a new Nintendo marketing pamphlet gives us the tiniest of morsel to feed on. You can read the blurb from the pamphlet below.

Finally, Link and Zelda return in the eagerly awaited successor to unforgettable action-adventure The Legend of Zelda: Breath of the Wild, with series producer Eiji Aonuma promising a darker adventure this time. Deep within the caverns beneath Hyrule Castle, a new and powerful threat awakens. Can our courageous heroes save the kingdom again?

Not a mind-blowing statement by any means, but always nice to have a confirmation. What were Link and Zelda doing in the caverns below Hyrule Castle to begin with? How much of the game will involve working our way through this underground hollow? Hopefully Nintendo shares more insight soon.