Wights ... hell yeah.
Even better is the Wight Claw Graft from Open Grave.
You can stick it on a monster,
without generating the ~costs, that a PC would get (the penalties in the brown box)
works just like the Wights normal attack (give or take)
and it doesn't increase a monster from standard to elite, or elite to solo, or solo to solo+.
It's free.
Well, you can see it easily, and it looks like a Wight claw, and that can be ID'd by the appropriate Monster Knowledge check.
PCs don't get much out of this.
Monsters have 1, 2, or 3 Healing Surges per Tier.
So you could hit a monster for 20% of it's real hit points, once at heroic.
You could hit a monster for 16.6% of it's real hit points, twice at paragon.
You could hit a monster for 14.3% of it's real hit points, three times at epic.
But this is only useful IF , and it's a big if ...
the monster(s) have Second Winds, or Potions, or Class Templates, or Tricky Items they are the guardians of.
Meh.
Monsters otoh ...
wow, they can really gank a party's hit point and heal surge pool.
Of course, once those Heal surges are gone, a Wight / Wight Claw isn't doing much else.
Still knocking out more than half of your hit points rather easily, is kinda Horror-ific.
Wight Claw + ShakaUVM's Intimidate set-up = I wonder how that works ??