War Chest, StarCraft II’s seasonal program that gives players a way to unlock an arsenal of in-game extras while supporting StarCraft II esports, is back with all-new rewards with War Chest 4! Additionally, for the first time ever, War Chest will integrate directly with social video service Twitch to reward players for watching StarCraft II on the platform. Players who watch participating StarCraft II streams on Twitch during War Chest 4 will earn XP towards unlocking rewards, just as they do for playing the game.
War Chest 4 rewards are themed after Terran Special Forces, Simulant Zerg, and Forged Protoss, and they include in-game player portraits, sprays, emoticons, banners, and—for the first time—building skins.
Players can purchase access to War Chest 4 for €9.99 (EUR) per race or €24.99 (EUR) for all three races. 25% of the proceeds will fund 2019 StarCraft esports. War Chest 4 kicks off December 18, so stay tuned for more details!
War Chest 3 increased the prize pool for the 2018 WCS Global Finals at BlizzCon by $200,000, bringing the total prize pool to $700,000—tied with the highest prize pool ever for a StarCraft II esports event.
Source: StarCraft II BlizzCon 2018 Fact Sheet
Edit 2018-12-20: You can buy the Warchest through affiliate links to support your favourite streamer!
Here is a list https://www.twitch.tv/team/sc2warchest/