s7e19 “Strange Bedfellows”
Worf has a real knack for this sort of thing.
If the last door is Weyoun 7 (pictured above), then 5 (background) had a mysterious “transport accident” (at the hands of Damar) and 6 (middle ground) was the traitor who died helping Odo.
Those two are like a bitter old couple in a dead marriage. I love it.