Quickening Fog causes a smoke bomb to be dropped at the end of your dash. It correctly triggers effects tied to smoke bombs only in some instances. For instance the Trickery Malignant Heart works but the Revenge Malignant Heart does not. Both hearts should be triggered by a subterfuge skill (smoke bomb, even though it isn’t cast directly)
I did some testing and looks like it needs a related skill on the hotbar to function. So for rogue you would need something like poison trap or dark shroud on the hotbar for it to work. I really hope that’s a bug and not the intended outcome.
That would be interesting behaviour if true. The trickery heart does work without smoke bomb in the skill bar though.
Edit: just tested putting smoke bomb on the hotbar and now both hearts trigger as expected. There is still inconsistency in how the hearts operate, and I believe for other effects of similar type (i.e. a skill being augmented with another skill) you wouldn’t typically even need to have that second skill unlocked in your tree for it to work, let alone on your hotbar.