Sombra is a character that has been teased in Dorado for a while now. Lots of theories have been made about her, but up until recently there has been no real content about her existence.
The Game Detectives wiki has a full recap of the ARG, and I'd recommend giving their page a read. The gist of it is:
JULY 12: The Ana Origin Story video is released, has hexidecimal codes hidden inbetween scenes
JULY 19: A dev update video has weird TV interference at the end; it's a bunch of bar codes that form a QR code
AUGUST 2: Summer Games video goes live, secret code found in Tracer's blink that needs a code, characters have cardinal directions in the background that form a full compass
AUGUST 11: Every player profile receives a strange achievement on the PlayOverwatch website. The page source has a code that uses the compass as a password and leads to another corrupted image, this time with an ASCII skull in it.
AUGUST 23: A forum user named 'Skycoder' posts on the Blizzard forums. In the page's glitching, the code for a new ASCII skull can be found. Comparing the ASCII skulls reveals a URL for a video. The video has a message in the pulse monitor that translates to 'momentincrime'. Emailing tips@amomentincrime gives another code that refers to specific characters in each skull. This gives us 'SOMBr@1NF:rM@7iON1SP0vvErrSOMBr@'.
AUGUST 24: amomentincrime.com has a percentage slowly rising. It's currently around 8%.
- Invite to the Sombra Discord server
- Game Detectives Wiki recap
- Skycoder's post
- Guess the Tracer code password
EDIT 1: removed part about the 'hacked' twitter accounts, as the sombra discord has concluded that they arent real? but ill keep an eye on them
EDIT 2: @BlizzardCS confirmed that they aren't real. :(