This article is strictly for those of you who are caught up on all the episodes of “Lost,” most importantly season 5. If so, THR has just released a casting brief, which centers on one of the most mysterious villains on the island. He’s so mysterious that we don’t really know anything about him, including his name.

Spoilers are featured below:

Remember last season when Jacob was shown on the beach with a man who many viewers dubbed as Esau or The Man in Black? He was obviously the evil balance to Jacob’s good and was played by actor Titus Welliver. According to the trades, the actor will make a return in the second part of the final season, which is interesting since speculation has it that he’s no longer in his regular body. Do I smell a flashback?

At the end of last season the character assumed the appearance of a dead John Locke, and manipulated Ben into stabbing an unsuspecting Jacob. Hopefully his return will answer the question of how he took possession of Locke’s body, and what his true motives are regarding the island and its inhabitants. He’s just one of the many returns we can expect to see along with Emilie de Ravin, Cynthia Watros, and Harold Perrineau.

Season 6 of “Lost” airs on ABC on February 2.

What do you think Jacob’s nemesis has in store for the castaways? How do you think he got into Locke’s body?