It also works if you killed Stilton, as his house will be under new ownership.

In that instant of interacting with Stilton you changed the present, and realising it is one of the most exhilarating moments in gaming. The Bloodflies are gone and the house is pristine. A servant is nearby, working and talking to themselves, or perhaps they have noticed you and are threatening to call the guards. You emerge in 1852 again, and suddenly hear voices. Because when you do something incredible happens.

However the spirit of a nihilist run is definitely 'no powers or gadgets', and the timepiece counts as either a gadget or a power depending on how you look at it (its a left-hand item). There are a lot of guards in the open garden area where Stilton is found, with easy line of sight to him, and I believe this is to make it likely that the player will either kill Stilton or knock him out and then quickly flee back to the present. Stealing the Master Key is probably the hardest part of the whole mission, if you go that route, so if youre wanting to pick the easiest route, go with the timepiece. If you ignore him he will attend it and his fate remains unchanged, and if you kill him his house is bought by someone else and renovated.

If you choose to be merciful and leave Stilton alive, but choke him out, he misses the seance and never becomes traumatised.

Kitchen key dishonored 2 mission 7