No revenue estimate for GOG — its rating/review counts don't calibrate to sales the way Steam's do. The Steam version is estimated at $5.6M — a different platform, not this one.
Styx: Master of Shadows
Styx: Master of Shadows is an infiltration game with RPG elements taking place in a dark fantasy universe, where you sneak, steal and assassinate your way through as Styx, a Goblin two-centuries of age. Deep inside the vertiginous and multi-layered forsaken Tower of Akenash, where Humans and Elves protect the World-Tree, source of the Amber – a powerful and magical golden sap – is hidden Styx’ chance to understand his true origin... and to make a fortune at the same time. Prowl through the huge, miles-high Tower of Akenash, completing various missions (assassination, information recovery, etc.) and avoiding detection. Progress in the shadows, assassinate your targets in close combat, or orchestrate «accidents». RPG mechanics let you unlock new powerful skills, impressive special moves, and an optimized equipment. Amber will grant you spectacular powers such as invisibility, «amber vision», and the ability to clone yourself. Explore the levels to discover every bit of information about your past, and steal prized treasures to acquire equipment upgrades. Embrace the shadows! Mission areas featuring truly organic player path-finding A strong focus on hardcore stealth and infiltration: progress through the shadows with a sense of verticality, and explore to find hidden treasures Upgrade your skills along six unique skill-trees to improve your stealth, assassination, and technique. Distract, solve, smother and prowl with your clone An intricate story full of twists and revelations