I'd like to post a suggestion for Phantom of the Operating Room..
The Ghost Breakers can be easily avoided by possessing them, since it's not necessary for them to flee in this particular level. Just bind ghosts with the appropriate power and use the 'Pick on' order. You can avoid wasting plasm once they're possesed by ordering them to pick on members of the opposite sex.
To keep it simple, you only need Weather Witch, Aether, and Wavemaster to accomplish the goal. Add Arclight if you want to free Sparkle (bind him to the nearby corpse and use 'bonfire').
The combined powers of rain, gusts and gather winds will clear the fog from the island and knock over the nearby tree.
Use Blair Wisp's 'hypnotic image' to attract the mortals, which will free him. Bind him in front of the fallen tree and continue to use the hypnotic image. As the mortals approach the tree, activate Darkling's 'obsession' power and they'll head right for the cellar.
People, People! Ye of little mind. My team: Whisperwind (For clearing haze) Weatherwitch (For clearing haze) Cogjammer (I'll tell you, but you need Fools Errand/Wild Geese) Arclight (Sparkle) Terroreyes (Ice Breath) Knuckles (Ice Breath)
Basically, start by freeing Sparkle with Bonfire. Then clear the haze with WW and WW, then talk to Blair Wisp. Use his Hypnotic Image, until a person looks at Blair Wisp. If not, retsart. Use Quake by that incredibly useful perched tree in the gorge thing. Then use Ice Breath with TE and Knuckles. Then, fun part, bind Cogjammer to a headlight, and then use Fools Errand or Wild Geese (Wild Geese better because they all go) They should run all the way to the Darkling. Use Obsession to lure them in entirely if they don't go all the way in. Peasy! With MS, just use Spooky Suprise!
In Unusual Suspects, I finally managed a sub-20 minute time (17:14) by using Hogwash, Cogjammer, Static and Firetail, along with Stonewall (for Banzai and of course my main gun: Clatterclaws. I reasoned that the level has electrical fetters everywhere, so I loaded up on electrical fetter ghosts. Of course I freed Electrospasm first off, then used his Surge power to unlock the cells with the crooks and frat boys. Mass gzot! Much plasm!