I'm running the Beyond Life and Death mod. LH 1.8.
Had 7 heroes in my big conclave (5 were henchmen, and four of them and one of the champs had just gotten back with good gear for the guys who lived in the conclave) and got attacked. City had Wall of Fire and Pit of Madness on it, and I had Arcane Weaponry and Companies, so I wasn't too worried. Clicked manual because I wanted to watch and see how the wall and pit messed up the attackers.
Only my militia + ninjas (had temple of secrets there) and 1 henchman showed up for the fight. Pit of Madness and Wall of Fire did not trigger.
On the completion screen after I slaughtered the attackers anyway, it declared that all the other heroes had died. Yet there was no mana loss for the sovereign dying (who was definately one of them.) All the others picked up an injury, and the lot of them were immobilized and at 1hp afterwards.