- Ghost- These are ridiculous. Seeing it sends half the party screaming in save-induced fear unless they're tall enough to ride the Spookycoaster (ie, high level) and if you do actually fight it, it can possess people or wither people to death via the aging tables. BFRPG simplified the withering to be con damage and the appearance of aging, which is honestly less cool, but dang.
- Ghoul- 3 paralyzing attacks and attacking from surprise if they can manage it. Elves are immune to ghoul paralysis, which means they can get ripped apart the old fashioned way while all their buddies are down by packs of 2d12(AD&D) or 1d6 (BFRPG, though lairs still have 2d8). There's no 'cure paralysis' spell so, uh, screw you I guess. I've used ghouls some. They're bad news.
- Mummy-Tough,immune to normal weapons and resistant to magic weapons, nasty heal-denying disease, fear aura (but paralyzing fear not run away fear). Again, yikes, though at least they're relatively easy to kill with fire.
- Wight- Only magic weapons need apply, suck away your levels.
- Wraith- As wight pretty much, but they also float through walls and fly.
- Vampire- A hodgepodge of nasty abilities, mostly eclipsed by level drain in terms of what players fear. Also comes with weaknesses, at least.
- Shadow-Not undead, psych
- Zombie+Skeleton- The only undead that isn't a complete nightmare to fight.
And y'know, I think this is bad, because it conveys bad info to players by having the weakest undead be totally different from the 'real' undead.
"Careful," some session one NPC says to your new players, there's "Undead in them there crypts!" The players ignore the warning, rob some tombs, and either 2 things would happen
1- They fight some skeletons and zombies and learn that undead are slow, stupid, resistant to certain attack forms, but easily killed, all in all. Maybe the priest uses Turn Undead and gets a little moment to show off.
2- They get totally murdered by Ghouls or worse. Note that 1 naturally leads into 2, because fighting zombies and skeletons teaches you jack shit about the true face of the undead, perhaps the worst lesson being the false hope that turn undead will do diddly squat. Skeltals and Zombos aside, you need to be like 3 levels higher than any undead you're facing to have a hope in hell of Turning them.
Approach 1- Make the greater undead less horrifying.
- Ghoul- Ghouls can do a Claw or Bite for 1d6 damage, OR a lick for 0 damage but a chance of paralysis.
- Wight-- Wights can be chopped up by normal weapons, though they still drain levels. Maybe give a save vs level drain. Maybe change level drain for something else, like cursing or aging you. Personally I'm all for mechanics that scare the players, but level drain has a lot of annoying mechanical problems with it. BFRPG has negative levels as a sort of debuff that I think is a good compromise, but I'm getting distracted.
- Mummy- As is- they are hard to kill, scare the hirelings, and do something nasty if they get you, BUT have a weakness-fire.
- Wraith- As wights, but now regular weapons don't hurt 'em and they can do ethereal things. Maybe give them a possession attack, to warn about vampires and ghosts. Their weakness of becoming powerless in sunlight is harder to exploit but important to remember-BFRPG dropped that from the AD&D description which I think is a hella mistake. If you can't flee to the light of day, anyone who meets a 80 'flyspeed ethereal wraith with no magic weapon doesn't have a lot of options besides going 'well, if I kill myself before I get leveldrained, if I'm raised I'll be in better shape and won't turn into a wraith.'
- Vampire- I got my own thing with vampires but ignoring all that, all the other undead do sort of culminate with this- they can charm(possess) you, you need magic weapons, and they can do permanent damage to your dood, but they have other weaknesses too. Vampires are great because while they'll murder you in a straight brawl, you can come up with plans to defeat them without it coming to that. Maybe.
- Ghost- Honestly, this is a lot like a double-wraith with extra save vs spells style attacks. I'm not a fan. It seems like as the undead get nastier, the possibility of them talking also increases somewhat, so ghosts with unfinished business that can be bargained with (maybe like, possess me and we'll get vengeance on your killer) sounds good to me.
Approach 2- Make the lesser undead MORE horrifying
Zombies- Give them spawn creation and a gross special attack related to how they died. Drowned corpses vomit down your nose to drown you. Flaming zombies spread fire. Zombies slain in battle wield weapons unsheathed from their guts. Zombies dead of plague spread it, old zombies that died peacefully add 1 year of age if they touch you. Zombies so hideous they cause fear. Zombies glowing with runes that cause Paralysis.
Skeletons- Introduce intelligence and speed. Skeletons archers are a thing because trying to return fire doesn't work. Skeletons trigger traps on you. Skeletons can outrun you because they're so light on their feet. Skeletons use their ribcages to store giant poison vermin. Skeletons kill you with bone-puns everyone has heard already.
These approaches make the undead more of a proper learning curve and less of a learning curve with a pit trap on the 3rd step that drops you off a learning cliff. Also makes zombies and skeletons more interesting so you don't have to be all 'aha u thot this was a skeleton but it's a Huecuva'