News of Ghost Rider's introduction in Agents of S.H.I.E.L.D. Season 4 came as a shock to most fans -- especially since the show skipped Johnny Blaze and brought in Robbie Reyes, a relatively new character to Marvel Comics. Though the character didn't have a long history in the comics, S.H.I.E.L.D. managed to find a way to build the beginning of the fourth season around this new Spirit of Vengeance. After a mere ten episodes, however, the character was sent off to another dimension, but Reyes is set to return once more in the Season 4 finale. Ahead of this finale, ABC has released a few promotional stills featuring Gabriel Luna's return as Robbie in "World's End."

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The stills also suggest that Mack's story isn't quite finished yet. Though he chose to remain in the Framework, wanting to remain with his daughter Hope who died at birth in the real world, it appears there's a chance he'll return to the world outside of the Framework. Whether or not Hope makes it out with him remains to be seen.

According to the episode synopsis,

With the surprising emergence of Ghost Rider, Coulson and the team attempt to stop Aida from ending the world on the exciting season finale of “Marvel’s Agents of S.H.I.E.L.D.,” TUESDAY, MAY 16 (10:00–11:00 p.m. EDT), on The ABC Television Network.

"World's End" was written by Agents of S.H.I.E.L.D. executive producer Jeffrey Bell and was directed by Billy Gierhart.

Airing Tuesdays at 10 p.m. ET/PT on ABC, “Marvel’s Agents of S.H.I.E.L.D.” stars Clark Gregg as Agent Phil Coulson, Ming-Na Wen as Agent Melinda May, Chloe Bennet as Daisy Johnson, Iain De Caestecker as Agent Leo Fitz, Elizabeth Henstridge as Agent Jemma Simmons, Henry Simmons as Agent Alphonso “Mack” MacKenzie and John Hannah as Holden Radcliffe.