Arrow Season 5 has yet to premiere but Stephen Amell is already teasing the show’s 100th episode and The CW shows’ crossover.

Amell shared on social media a sneak of what fans could expect. He posted a series of photos with the characters that will appear in the biggest 4-way crossover on television. The crossover happens to be Arrow’s 100th episode too.

One photo showed the Green Arrow standing on the rooftop alongside Supergirl (Melissa Benoist).  In another, Oliver Queen is sitting on a bench beside Deathstroke. The most recent image showed Amell with Grant Gustin (The Flash/Barry Allen). Also with Amell and Gustin are actor Victor Garber (Martin Stein) and Franz Drameh (Jefferson Jackson/Firestorm).

Showrunner Greg Berlanti earlier talked about the crossover of four CW shows to Indiewire. He said: “We’re telling one cohesive story. Supergirl will participate, but the storyline doesn’t actively begin there. There are some characters who show up in her episode, but the story begins with The Flash episode and goes to Arrow and Legends of Tomorrow. We’re just getting into designing the bad guy for it, and we start now but it doesn’t air until the end of November.”

Apparently, the crossover between Berlati-produced series will feature a threat that will force Supergirl to travel to Earth. This is not the first crossover for the superheroine though. The Flash has made a cross-network crossover with Supergirl when Benoist’s show was still on CBS.

Who is the villain in Arrow Season 5 crossover?

The Hollywood Reporter wrote that The CW superheroes will unite to battle alien-raced villain, The Dominators.  The character was inspired from a DC crossover in 1980s known as Invasion!.  Arrow executive producer Marc Guggenheim revealed they are using state-of-the-art prosthetics for the villain character. Some cutting-edge computer effects will be used as well to achieve a film-quality look of The Dominators.

Arrow Season 5 premieres on Wednesday (October 5) at 8 pm on CW.

The Flash Season 3 will debut on Oct. 4 at 8 p.m., a day earlier than Arrow Season 5. Supergirl Season 2 premieres on Oct. 10 at 8 p.m. and Legends of Tomorrow Season 2 first episode airs on Oct. 13 at 8 p.m. on The CW.