Overwatch now has its first-ever Player-vs-Environment content, available for a limited season and based around Halloween.

The Overwatch Halloween Terror, as it's called, is a four-player cooperative mode that pits players against waves of enemies led by new character Dr. Jamison Junkenstein.

Enemies include repurposed and twisted Overwatch heroes, as well as "a host of shambling zomnics," while players can take the roles of Ana, Hanzo, McCree, or Soldier 76.

The event also includes new jack-o-lantern loot boxes with Halloween-themed cosmetic items.

Along with activating the event, the shooter's latest update brings a new leaderboard feature to the game; improves camera functionality in Spectator mode; rebalances Ana, Widowmaker, and Junkrat; and fixes the usual laundry list of bugs and balance issues.

Blizzard also announced that Overwatch now has 20 million players after five months of release, making it easily one of the year's biggest sellers.

Overwatch Halloween Terror is live now and concludes on November 1st.