Question: What is the "universe" featuring 25 playable characters in the first-person shooter video game "overwatch", published by Blizzard Entertainment?
Context: Tracer (also known by her real name, Lena Oxton) is a player character appearing in the 2016 video game "Overwatch", a Blizzard Entertainment–developed first-person shooter, and its related animated and literary media.  Tracer is from the "Overwatch" universe, but she was introduced as a playable character in Blizzard's crossover multiplayer online battle arena game, "Heroes of the Storm", in an April 2016 update. Winston is a player character appearing in the 2016 video game "Overwatch", a Blizzard Entertainment developed first-person shooter and its related media.  Winston is one of the more prominent characters used by Blizzard in "Overwatch" media outside of the video game; the character made an appearance in the game's cinematic trailer and is the focus of an animated short released by Blizzard. Blizzard Entertainment released several computer-generated cinematic trailers and teasers, as well as animated shorts, to promote and develop the story for their 2016 first-person shooter video game, "Overwatch".  The shorts have been met with positive reception from fans and online publications alike. Overwatch is an American digital comic series published online by Blizzard Entertainment and republished by Dark Horse Comics' digital service, featuring events surrounding the characters of the "Overwatch" universe.  The title was launched on April 21, 2016, and has continued to be published with no set schedule. Olivia ""Sombra"" Colomar is a character in the fictional universe of "Overwatch", a 2016 video game developed by Blizzard Entertainment, and the subject of a related alternate reality game (ARG).  Throughout the game's open beta, clues regarding Sombra were placed into a map called Dorado, a fictional town in Mexico.  Hints about Ana Amari were placed into another map at the same time, and confusion over the two led initial speculation believed the two were a single character.  The alternate reality game continued through November 2016, spanning official Blizzard videos, the Battle.net forum, websites representing fictional entities in the "Overwatch" universe, the game itself, and the "Overwatch" subreddit. BlizzCon is a video game convention held by Blizzard Entertainment to promote its major franchises Warcraft, StarCraft, Diablo, Heroes of the Storm and Overwatch.  Since October 2005, it has been held at the Anaheim Convention Center in Anaheim, California.  The convention features game-related announcements, previews of upcoming Blizzard Entertainment games and content, Q&A sessions and panels, costume contests and playable versions of various Blizzard games.  The closing night has featured concerts by The Offspring, Tenacious D, Foo Fighters, Ozzy Osbourne, Blink-182, Metallica, Linkin Park, and "Weird Al" Yankovic. Mercy is a player character appearing in the 2016 video game "Overwatch", a Blizzard Entertainment–developed team-based first-person shooter, and its related animated and literary media.  Lucie Pohl voices Mercy in English-language "Overwatch" media. Overwatch is a team-based multiplayer online first-person shooter video game developed and published by Blizzard Entertainment.  It was released in May 2016 for Windows, PlayStation 4, and Xbox One. The team-based first person shooter video game "Overwatch", developed by Blizzard Entertainment and released in May 2016, features 25 playable characters (heroes) and a number of supporting characters as part of the game's narrative, which is told through animated media and digital comics outside of the game. Hanzo Shimada (Japanese: シマダ・ハンゾー , Hepburn: Shimada Hanzō ) is a playable character appearing in the 2016 video game "Overwatch", a first-person shooter video game developed by Blizzard Entertainment and its related media, which includes animated shorts and webcomics.
Answer: characters of the "Overwatch"