In a comment to an earlier post on the length of combats in 4e, the ChattyDM made a very good point. A lot of the problems with the game can easily be dealt with by adjusting monsters. One of the core aspects of 4e is that it is exception based. The monsters literally can do anything you want. There isn't any need to keep the base powers, or the base damages.
I'll be expanding on that point in the next little while, but in the meantime I wanted to reintroduce one the elements of earlier editions that truly frightened PCs: Energy drain.
For good reason, Energy Drain was removed from the core game. However, there is no reason one can't easily put it back in. You just have to figure out the mechanics for it.
The Death Wight is based off the Battle Wight, but with a critical alteration to it's main attack power. I have no idea how nasty this would be in practice, but I wanted to use the new Death Save mechanic but also bring in the threat of a level loss. I think it's still fairly unlikely. First, the wight has to hit...then there needs to be a failed death save. Then you need to fail another save at a +5 bonus. For each hit, there is a 1/8 chance to lose a level. With three failed death saves the PC dies anyways (which is another way to scare the pants off the PCs...the threat of sudden death).
That probability might still be too high. If you use this you should also create a Ritual which would be the equivalent to Restoration from earlier editions.
As a bonus, if you really want to scare the crap out of your players, add in a Deathterror Wight, which is based off the Deathlock Wight, with an added aura of nastiness which really syncs with the Death Wight.
What do you think?