The movement felt a little clunky at first, especially the climbing, but once I got used to the controls I quite enjoyed it. It was a pretty entertaining stealth game with an original main character, a charming antihero that added a lot of personality to an already decent story.
Although a little repetitive, the level design was rather good, with multiple paths to reach most places, a lot of verticality, and a few secondary objectives to add an extra motivation to pay attention to the layouts. Most of those optional objectives were a bit too simple and uninspired, but I liked the ones that involved looking for a relic hidden someplace in the map with the help of some clues.
All in all, while not the best and with some uneven moments, it was a rewarding stealth experience. Exploring the levels to quietly find the best way to reach an objective was always quite fun, and lurking behind the shadows to study a guard's route or jumping from ledge to ledge, waiting for the best time and place to eliminate an enemy below you without being seen or heard, never got old.
More info: https://en.wikipedia.org/wiki/Styx:_Master_of_Shadows