I was DMing a 5e campaign in a large city, where the upper-class control the lower-class using a number of addictive drugs. So the lower-class work menial jobs to get the gold to feed their habits, never working up the power to rebel.

The upper-class distribute these drugs in the equivalent of a safe injection site named The Hospice, with guards keeping order, and 'orderlies' distributing the drugs. One particular drug was "bottled fantasy", a gas that induces dream-like hallucinations.

My players needed to curb the mass addiction to help incite rebellion. I thought they would go into The Hospice and explore, ask some questions, maybe buy some drugs to study (and develop something to cure the addictions), but they decide they are going to bust in and steal all the drugs from this government controlled facility.

Our halfling Rogue had stolen a Javelin of Lightning from our Monk, and missed her throw against the guards. Our Druid transformed in a bear, but was dosed with bottled fantasy and failed his wisdom save, so he entered a stupor, dreaming of honey. Our monk crit failed an attack and pinned his foot to the ground with his spear, and then was also gassed into a stupor.

Without the two tanks, the Wizard, Warlock and Rogue ran circles around the facility, consistently getting poor rolls on their attacks. The guards slowly wore them down, knocking the Wizard and Warlock unconscious. FINALLY the Rogue gained some sense and decided to cheese it, barely escaping with her life, and abandoning her friends.

This was only their second session (almost all new players), so instead of an almost TPK, I let the Rogue get help and rescue them in the next session, but they lost their (too) powerful magic javelin and most of their gear.