'Arrow' season 5 release date, plot spoilers: Stephen Amell teases the return of Deathstroke in the 100th episode of the show

The fifth season of The CW's "Arrow" will hit the 100th episode milestone this year, and it looks like famous Batman rogue Deathstroke will be making an appearance.

In a Twitter post by "Arrow" star Stephen Amell, he posts a photo of himself sitting on a bench next to Deathstroke. The identity of which actor is playing Deathstroke, however, is still a mystery.

Some fans speculate that the person under the mask would be the original Deathstroke, Slade Wilson, played by "The Hobbit" actor Manu Bennet. Then again, the last season of "Legends of Tomorrow" had an older Green Arrow talking to another version of Deathstroke which turns out to be Slade's son, Grant Wilson (Jamie Andre Cutler). Is the Deathstroke in the picture the original? Or is it his estranged son from the future?

Deathstroke already has a long history established on "Arrow" and he has been in the universe since season 2. His return will definitely mark something important as he is one of the few characters to know Oliver Queen before he became the hooded vigilante of Star City.

Another familiar face is set to return as Jamey Sheridan will guest star in the 100th episode as well. He played Oliver's father Robert Queen, and he was suspected to have died in the accident that left Oliver stuck in Lian Yu. The showrunners, however, hint that his appearance will have nothing to do with Flashpoint or any sort of Flashback, so fans can expect an interesting twist.

It also looks like Deathstroke is getting more exposure lately. Joe Manganiello has been cast as Deathstroke/Slade Wilson in Ben Affleck's solo "Batman" movie, and it would mark the character's first appearance in the silver screen. The character seems to demand actors of an intriguing physique as Manganiello and Bennet are known for their towering structures.

"Arrow" season 5 premiere will premiere on Wednesday, Oct. 5, at 8 p.m. EDT.