I'll be ramping up my middle school Dwimmermount campaign again this month, so I've taken a bit of time to reflect on how I'd like to approach things.
While pondering undead, I thought, "Hey, what if there are only seven types of undead; one for each of the seven deadly sins?"
Undeath is a curse of continued earthly existence for those souls dominated by their particular vice.
Hmm... let's start with the easy ones:
Gluttony = ghouls
Lust = vampires
Wrath ... I like wraiths for this one, but, because of Trampier's Monster Manual illustration, I've always modeled my wights after Iron Maiden album covers ... images that are completely defined by their violence.
Greed ... what about mummies? Rather than being mindless guardians or tragic sentries who stand to their posts beyond death, they are souls dominated by brooding over wealth which they can't bear to leave behind.
Envy (I hate you because of what you have) ... ah, this is where I can drop wraiths. They hate you because they are dead and incorporeal; they hate you for your warmth and life. Incidentally, I never really got the point of specters in D&D. How are they materially (heh) different than wraiths? I'll just lump the two in together--some are nastier, some a bit less.
Sloth is tricky ... how about shadows? I know in the oldest published D&D materials they aren't undead, but so what? Shadows drain Strength from their victims (permanently in my games); maybe it's a side effect of their surrender to laziness.
Pride, the most deadly of the sins = lich
Okay, where does that leave all those other undead who've crept in over the years and editions?
Well, sins are an act of the will so if it doesn't have a will of its own then it isn't a "true" undead. Skeletons are just magically animated bones. A wizard could just as easily use straw dummies, shaped clay, or whatever (same stats). Such mindless constructs aren't inherently evil (neither is their creation) and cannot be turned by lawful clerics.
Ghosts ... man, I always felt like D&D missed the boat on these compelling critters. A medium-level enemy with a weird aging effect (that elves and dwarves can pretty much ignore). I think for my purposes 1.) ghosts generally don't exist, 2.) they are lumped in with wraiths, 3.) they are mindless psychic shadows and residual emotions sometimes left behind (like the later "haunt" from Monster Manual II).
As for the rest, they drop pretty easily into the categories above or get dropped.
Death Knight = big nasty wight
Flameskull ... no ... just no ...
Crypt Thing = lich with a sense of humor
Huecuva ... has anyone ever actually used one of these?
Banshee = fairy, not undead
Coffer Corpse = strangley ghoul ... you get the picture.
Of course each broad category has room for variety ... some vamps drain hit points, others Constitution; some have 10 hit dice, others 15, etc.
Has anyone tried something similar?
Part of the appeal is that the adventuring party has a reason to ask around about the old lord and his habits before tromping up to the castle to deal with him. Was the old coot especially greedy or did he sit idly by while folk under his protection were plundered? These could be clues that will help the group anticipate what they may face.