The Humble Store's Spring Sale is currently running, with huge discounts on over 4,000 games across the store. One of the perks of the sale is "Ashes Of The Singularity: Escalation", a free-to-grab game on your pilgrimage, and this time Ashular of Singularity: Escalation, Stardock's large-scale real-time strategy game, will be free until Sunday.
To claim the free game, you have to sign up for the Humble Newsletter and you will receive a Steam key in return. You will be able to add the game to your library after activating the key, but the code must be redeemed before May 14 or it will not be available.