Blizzard will be at Gamescom 2017, and they aren’t showing up empty-handed. They’ll have a slew of announcements for many of their titles during the Blizzard Reveal Ceremony, slated for August 21 at 6:00PM CEST, or 9:00AM PDT. Convention goers will also be able to try many of these game content updates more on the Gamescom show floor.
First up, Overwatch will get a new map, and an animated short will be unveiled:

The world premiere of a new Overwatch animated short will take place on our main stage and via live stream during the Blizzard Reveal Ceremony on Wednesday, August 23.
Visitors to the Blizzard booth will be able to experience a brand-new Overwatch map?tune in to our preview video on Monday, August 21 when details will be revealed.
Diablo III will have Rise of the Necromancer on the show floor for demoing:

Attendees at gamescom will be able to command legions of the risen dead and wield the dark arts with Diablo III?s Rise of the Necromancer pack, playable on PC and PlayStation 4.

Many of their PC only games will also have a presence:
Hearthstone

Hearthstone players can enjoy an early look at new Fireside Gathering features during gamescom, where they?ll join forces in a whole new kind of Fireside Brawl: a group raid against the Lich King.
We?ll find out which country?s players will rise above the rest as the Hearthstone Global Games Finals take place live on our Hearthstone stage on Friday and Saturday, August 25 and 26

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