Iceborne‘s story begins not long after the end of the main MHW questline and sees your character headed into the frozen wastes, a new and unexplored frontier within The New World, to seek adventure and uncover its many mysteries.
You don’t necessarily need one, but I personally found it to be essential. Here’s the thing you should be very aware of coming into Iceborne - it is endgame content, by which I mean you will want to have a max level character that has cleared the campaign available to you or you won’t be getting the best the experience has to offer. Monster Hunter World: Iceborne goes all in, throwing a truly staggering amount of fresh content at returning players.
That something new could be an addition to the story, a new area to visit, or new moves and mechanics. Ideally, a good expansion pack extends the life of a game with something new.