Fans are likely to witness some shocking developments in 'Arrow' Season 3 episode 21 titled 'Al Sah-Him.' In fact, the upcoming episode of 'Arrow' Season 3 is being touted as one of the most exciting episodes on The CW, where fans will see a superhero turning into a hardcore villain.

According to IB Times, the official trailer of 'Al Sah-Him' is packed with plenty of action, twists and turns. In the upcoming episode, fans will possibly see Oliver Queen (Stephen Amell) turning bad, and may even become the Assassins' leader by accepting the offer of Ra's al Ghul's (Matthew Nable).

Nevertheless, fans of 'Arrow' will certainly not like Oliver Queen tuning into a villain. If he does, it will prove to be a disappointment for his die-hard fans.

Some spoilers of 'Arrow' Season 3 episode 21 have claimed that that Thea Queen (Willa Holland) may also turn evil due to psychological effects of Lazarus Pit's powers.

In the meantime, it is interesting to note that possible spoilers of 'Arrow' Season 3 episode 22 titled 'This is Your Sword' have already surfaced online. Episode 22 will be the penultimate episode before 'Arrow' Season 3 finale titled 'My Name is Oliver Queen.'

ComicBookMovie reports, "Oliver/ Al Sah-Him (Stephen Amell) finishes his training and is left with two final tasks to become the next Ra's al Ghul. Ra's (guest star Matt Nable) threatens Nyssa (guest star Katrina Law) and delivers some shocking news. Meanwhile, Malcolm (John Barrowman) makes a surprising offer to Team Arrow and Thea (Willa Holland) goes to see Roy (Colton Haynes)."

'Arrow' Season 3 episode 21 titled 'Al Sah-Him' will be aired at 8:00 pm Wednesday, April 29, on The CW.