I'll start with MM V And work my way back, then hit the splats.

These things are in:

Banshrae - Creepy musical fey? Works for me.

Blackwing - Dependent on necromancy. Could be an evil bound spirit forced into a bird, could be an ancient mount of a famous and powerful Wightspeaker, returned with him to defend the Vallheim. Undead =/= evil, but they aren't always good.

Burrow Roots - Eh, sure, why not. Deep forest, not in Mr. Roger's backyard.

Ember Guard - Sure, like a fire elemental spirit thing. Sounds good. Just ditch the evil parts.

Fetid Fungus - Ummm... Ok. Sure. It won't hurt anything.

Frostwind Virago - Yeah, fey are good. This one especially.

Golem, Magmacore - I imagine these are built by Solerian priests to guard their holy temples.

Graveyard Sludge - This is the tool of eeeevil necromancers. No hero-caller would use this.

Haunt, Bridge - The perfect sort of undead. I love it.

Haunt, Forest - This is also good.

Haunt, Taunting - Creepy, a little funny, all around decent.

Jaebrins - I suppose these guys deserve a little more inclusion. Wildwood men, lots of potential there.

Ruin Chanter - Oh my goodness, fey ruins sound like such a cool idea. This guy can guard them.

Shaedling - Tiny evil fey. I can dig it.

Spectral Rider - Very cool. I like creepy undead that aren't just dumb.

Thrym Hound - Maybe a wolf from the far north? I like these. Just lose the extraplanar crap.

Vampires - I'm iffy on these guys. Still pondering.

Verdant Reaver - Ok, yeah. Plant thing animated by the fey. Cool.

Wild Hunt - This is what epic levels should be. This is a god of the Vallheim, or something. The kind of thing you hear about in stories and that only comes out once every hundred years to hunt heroes.... Yes. It's freaking in.

So, that's MMV. MMIV Comes later today, probably.