I am able to destroy them easily on a moderately high difficulty with my full set of enchanted armor, yet they still can scare the crap out of me. Only the night mother in skyrim comes close to as scary as a wraith.

I think it is more to do with how far away their breathing is, and the music around them.... terrible creatures

I wouldn't exactly call it a scary design, although seeing one of them suddenly come out of the darkness....oh my(namely if you don't have the weapons to damage it, and your spells won't do very much). Still, I tend to find them a little annoying - mostly because of the sounds it makes when attacking it. Just like for a few other enemies in the game(mostly the creatures), I can't have any sympathy for something that is trying to kill me. Perhaps in this instance the Wraith isn't due for it, but then it should not be whining like that.

Actually, while it isn't vanilla, MMM adds a varient of the Wraith, that if it is spawned in a dungeon, it has one sole purpose - to paralyze you. It disappears once it does, but then you get left with a 3 minute paraylze effect(which doesn't last that long, but you are never sure how long it will be). Even worse? There is a sound clip that will play when one spawns, randomly, from the moment you enter the area. I've usually encountered this with no other enemies around, but once I had a skeleton whacking me while paralzyed. Good thing I had enough health to lose before the effect wore off(probably was only down by half or so before it did.).

I generally pay wraiths no mind. All but a few are willing to give up their secrets.

-Beckett

It′s fun to summon your own wraith and see them battle each other

I adored those things! I thought they were genuinely frightening. They were brilliant. In fact they were the only monsters in the game - vanilla or modded - that truly scared the pants off me.

The first character I saw them with was a Khajiit mage, likely somewhere around lvl 10(though I don't know if they only spawn past a certain level). Even when I first heard that sound, I felt like a cub at the moment, no spells, no staff, no weapons. The character had already been through the Kvatch quests(with MMM amping up the spawns in some places), and this had me wishing I had a tail to put between my legs.

Although, I have yet to see the infamous creature that the mod adds to the gates. Given that I have seen the Lesser versions, and how much time it took to deal with those(when not with powerful weapons/armor), I'll probably be sweating if I ever do see one. Of coruse, when I first encountered the lessers, I thought the sound was from the actual thing.

Most of the creatures MMM adds are startling, if nothing else(although some of the more higher level ones I haven't seen yet). However, the one instance I jumped, was probably with one of the obvious vanilla creatures. The Land Dreugh. I think I might've heard about it previously, but not really seen it outside the game.

Yes they are quite creepy and can be quite difficult to take down if you get 2 or 3 of the in a close proximity.

EDIT: NVM. I found out the problem.

They used to scare me but now I find them very annoying. Still, having them all up in your face screaming like that while they're trying to hack you to pieces can be unnerving sometimes.

I also think the wraith design is very good. Including the screams, and in particular the death scream when they exhale (ectoplasm?)

I've never done that. I like to summon Daedra against undead, and vice versa.

But I love summoning a wrath against some big Warlord or Xivilai and watch them try to battle it with their Ebony warhammers or such.

My only problem with summoned wraiths is that they often just float around without doing anything except looking scary.