Running an adventure which has a Trench Mist and number of Juju Zombies in the same room.
If the Trench Mist moves over the Juju Zombies in order to engulf the PC's would it also have to engulf the Juju Zombies and thus deal damage to them on their turns?
If it does deal damage would be be both the damage of the acid and then healing from negative energy damage?
as the zombies have to be engulfed to be controlled, and the information keep talking about it having the zombies as part of it's community ("A juju zombie becomes free-willed if it is separated from its parent trench mist"). i would assume it doesn't deal damage to something it doesn't want to (like the zombies).
also, going by raw alone, say it does deal acid damage that hurt them and negative that heal them. and say it does deal enough damage to kill them,again, once it kill them they rise again as juju zombies ;
"A trench mist can animate any corporeal creature that is slain while engulfed within the mist's form. The victim rises as a juju zombie in 1d4 rounds"
this also mean that any juju zombie the player's kill while still engulfed will rise again even if removed from the mist area after it's killed (if removed it will simply be free willed juju zombie, old edition ones even kept their alignment). as it doesn't say that the one killed must be killed BY the mist (like with say, vampires, only that it dies inside the mist.)
to fully kill them the players must ether first kill the mist or remove the zombies before they kill them off. (and this is so broken id add 3-4 to the cr of this creature depending on what zombies it have)
Engulf, unlike a swarm attack is targeted. So a trench mist doesn't have to deal damage to it's allies.