Shadow is an achievement/trophy in Dishonored, Dishonored 2 and Death of the Outsider.
How to Acquire[]
In order to get this achievement in Dishonored, Corvo Attano must complete all missions after the prologue without alerting anyone. In Dishonored 2, Corvo or Emily Kaldwin must never be detected.
The best plan of action is for the protagonist to take alternative paths and utilize sleep darts and Blink or Far Reach (especially with the Invisible Thread bone charm) to avoid enemies that cannot be passed normally. Other stealthy supernatural powers, such as Mesmerize and Possession, are also very useful.
The achievement also states that the main targets of the game must be unaware of the protagonist's presence, making the stealthy approach the only option.