Mastodon had stated time and time again that Emperor Of Sand was loosely the story of someone battling cancer, and that the story meant so much to them because they'd lost loved ones to the disease type. Now the band has opened up about their individual stories, and how cancer has affected their lives and the lives of those close to them, and it's a pretty difficult watch.
Definitely pick up Emperor Of Sand here. Aside from the album touching on a lot of emotional aspects, it's also an instant Mastodon classic.