Alekhine's Gun

To equip chloroform, press . To use it, when standing behind a target, hold and press to render them unconscious. You need to use chloroform on 30 enemies. Using chloroform does not count as a kill.

If you haven’t unlocked this by the end of the campaign (if you are trying to unlock “Legendary” in your playthrough you shouldn’t have), there’s a spot in Level 1, ‘Ghosts of the Past,’ where you can get this with minimal effort simply by reloading a save point.

At the beginning of the level, after you’ve changed into a German soldier outfit and walked across the courtyard to sneak inside the castle, turn right and walk through the door (do not go up the stairs). In the next room, walk around the U-shaped room and go through the only door. Keep to the right and walk through the first door on the right (there are two Germans conversing here). You are now at the room where we will farm this achievement. Make sure you close the door first, then pause the game and “Save Game.”

Outside the door in front of you is a guard. Before you open the door, press to equip chloroform. Open the door (but don’t walk through it), immediately walk to the left a few feet and click to whistle. Quickly make your way to the right of the door. Whether or not the door closes, the guard outside will investigate. When he walks into the room, walk up behind him, hold and press to drug the guard. Pick him up and in the dark corner of the room is a closet. Hide the body in there to count towards “Undertaker.”

When you’ve completed these steps, pause the game and “Load Game” (do NOT save over this slot). Select the file you previously saved and it will take you right back to that spot. Repeat until you’ve unlocked this achievement. When that’s done, switch to the garrote () and repeat the steps until you unlock “Go for the Throat” (keep hiding the bodies until you unlock “Undertaker”).