With Supergirl moving to The CW for its second season, the network is poised to have its biggest crossover event to date next season. A four-way crossover event is on the way this December with Supergirl, Arrow, The Flash, and DC’s Legends of Tomorrow all in the mix.

CW chief Mark Pedowitz made the announcement to reporters Thursday, calling the event “our biggest one ever.”

“Just imagine what our superhero crossover episode is going to look like come December,” he said. “Next season, Arrow, The Flash, Legends of Tomorrow, and now Supergirl will join forces in our annual crossover event, our biggest ever.”

This move is keeping in step with what the network has been doing over the past few seasons with Greg Berlanti’s superhero TV series. Arrow first introduced the idea in its second season when it brought in Grant Gustin as Barry Allen, following that up the next season with a crossover between Arrow and The Flash. This year, the two shows crossed over with DC’s Legends of Tomorrow prior to its first season launch, while The Flash also joined Supergirl on CBS.

(Via: Entertainment Weekly)