[SPOILERS for those not caught up on Agents of S.H.I.E.L.D. ahead.]
The first half of the season introduced the existence of supernatural forces via Ghost Rider (Gabriel Luna) and a dangerous mystical artifact; the Darkhold book.
D season 4, episode 12, “Hot Potato Soup”, a key ingredient is featured in the form of comedian Patton Oswalt; returning to his Marvel Cinematic Universe role(s) as agents Sam and Billy Koenig.