Songfacts®:

• Eminem's Revival album closes with the deeply personal trilogy of "In Your Head," "Castle" and "Arose". On "Castle," each verse finds Marshall Mathers writing a letter to his daughter Hailie in three different stages of his life; first December 1, 1995 (24 days before she was born), the second December 1, 1996, and finally December 24, 2007.
• The last verse is a letter written to Haille the day before her 12th birthday. It covers the period in her father's life when he was battling an addiction to prescription pills. Em raps about being overwhelmed with fame and quitting rapping for good.
  
  I can't stomach, they can take this fame back, I don't want it
  I'll put out this last album then I'm done with it
  One-hundred percent finished
  Fed up with it, I'm hanging it up, f--k it
  
  Em raps about being overwhelmed with fame and quitting rapping for good.
• Eminem explained the story behind the song In a December 15, 2017 radio interview on his SiriusXM Shade45 channel.
  
  "When Hailie was about to be born, I would always write letters I thought one day I would give her just to have 'em; that's kind of where the concept came from: Let me start from the beginning. And it goes into the addiction part; The 'Castle' song basically takes place in 2007, which leads to the overdose, which leads to Christmas and her birthday and me missing that because I was in the hospital.
  
  Me not being there for my kids for Christmas was rough. And if you listen to 'Castles' all the way through, you hear me taking pills and falling; that was the re-creation of me falling in the bathroom and then waking up in the hospital and not knowing what the f--- was going on. I had tubes in me, I was angry and I couldn't talk at all."
• The song was produced by DJ Khalil and features the vocals of Liz Rodrigues, who is a member of the producer's group The New Royales. The Toronto-based singer also appears on the Recovery tracks, "Almost Famous" and "25 to Life" plus The Marshall Mathers LP 2 cut "Survival."