Ni no Kuni 2: Revenant Kingdom's free Adventure Pack, which expands a dungeon and adds a new quest line, is out now.
The free DLC adds extra floors to the Faraway Forest dungeon and adds a "brand new story" in which Evan must defeat the Demon of Anguish. The quest line introduces two new bosses to fight—Blackhart and Zeta—and spans the whole game world.
The Adventure Pack also adds new items and outfits for Evan as rewards for both the quests and for beating the new, expanded dungeon.
It's the first of three planned expansions for the JRPG: the second adds a new "puzzling" dungeon, and is out this winter, while the third is a larger expansion that builds on the main game's story. That'll be out early next year.
You can purchase a $19.99/£16.99 DLC season pass for the game, which suggests that neither of the future DLCs will be free.