UPDATE: The game is now available free!
It's not the mystery game anymore as the leaked Twitter ad confirmed that Borderlands: The Handsome Collection is going to be this week's freebie on Epic Games Store.
The collection includes:
- Borderlands 2
- Borderlands: The Pre-Sequel
- all additional content released for the games
You can claim your free copy from 28th of May (17:00 CET) to 4th of June (16:59 CET) and keep it in your library forever.