The Monster Hunter series is famous for its crossovers, bringing gear and equipment themed around numerous other games. With Monster Hunter World proving to be a major success, it's now the Monster Hunter franchise's opportunity for a crossover in the other direction. During its E3 press conference, Square Enix revealed that Monster Hunter World content is on the way to its MMO, Final Fantasy XIV.
Square Enix offered a brief look at a forthcoming update. Patch 4.3 is called Under the Moonlight, and while we don't yet know all that it will add, one headlining aspect is Monster Hunter World-themed content. We saw a Palico companion in Final Fantasy XIV's world, as well as a Rathalos. It's unclear what the Palico will do or is, but it looks like Rathalos will be a boss fight in the MMO.
Under the Moonlight launches sometime during Summer 2018. It looks to be a completely free update, although you may need to own the Stormblood expansion pack in order access it. Of course, Final Fantasy XIV is a subscription-based MMO, so you'll need to have an active subscription if you hope to check out the new Monster Hunter content and whatever else might be added.