The Chicago rapper made it big with hit single "Lucid Dreams" and has since been a hot commodity. Marshmello, of course, has a history of working with MCs. He's made magic in the studio with Logic, Lil Peep, Juicy J and more.
There isn't much we know about the collaboration, other than that it exists. We don't yet have a title or a release date, or even a soundbite, but it seems to be finished, as Marshmello took to twitter saying he "can't wait to drop" the song.