In the "Complete these Encounters II", one of the challenges cited is to kill a monster possessed by two or more Tormented Spirits.
The thing is, in most maps I can usually find two or more spirits, the hard part is getting them to be close to each other and then both also moving the way I want so that the monsters get double possessed. But that seems like an incredible amount of RNG -- I've already done at least 150 maps and have yet to see two spirits ever spawn close enough to infect the same monster.
Is there an easier way to do this? Or am I stuck at the behest of RNG?