Nightmare Knight

Fight: the nightmare knight is a master in the use of the sword; he has a +3 to hit bonus and damage, which summed to the bonus geven by his Strength (18/51), becomes +5 to hit and +6 to damage. The sight of a nightmare knight causes terror: the first time he is met a ST versus Paralyis with -4 must be made, while for the following times the malus falls to -2. In a Ravenloft style campaign the DM might even impose a Horror check.

The sword of a nightmare knight is cursed: when it strikes a foe, this must save versus spells or be curse (see the invers of Dispel Curse); if the ST fails with a natural 1, the victim will be stricken by a lethal curse which will kill him in 2-8 days (only a Wish can save the poor one).
The nightmare knight feeds on people's emotions: in game terms he can use once every three rounds an innate power with the effects of the Emotion spell. To use this power the knight only needs to will it, so this power can be used at the same time as other attacks. Three times per day he can use any of the following spells at 15° level: Improved Phantasmal Force, Nightmare (opposite of Dream), Vampire's Touch, Shadow Magic, Dimensional Door, Hypnotism, Death Spell, Finger of Death, Wraithform, Transmission, Cold Touch, Shadow Door, Phantasmal Killer (7 times per day), Wizard Eye, Summon Shadows (1d6 shadows which appear instantly), Phantasmal Force, Fireball, Fear, Telekinesis. Additionally he can cast spells as if he was a wizard/cleric of the 7th level; he has access to the following schools of magic: Necromancy, Illusion, Invocation/Evocation, Summoning and, if the Player's Oprion: Skills and Powers are in use, the school of Shadow; and the following priestly spheres: Evocation, Sun (darkness spells only), Necromancy and Creation.
The nightmare knight can only be hit by +3 or better weapons, is immune to all shadow based magic (they make him recover 2d6 hit points), he has an 80% magic resistance and is immune to cold, frost, poison and gas. The Dream spell inflicts him 2d6 damage, while light based spells slow him for three rounds.
The light of the sun doesn0t kill him but it turns him forcing him to return to the Plane of Shadow in one round. The nightmare knight can't be turned.

Habitat/Society: Nightmare knights draw strength from the Plane of Shadows. The teleport on the Prime Material when darkness falls to torment the living killing them, if possible, with what they fear most.

Ecology: nightmare knights are powerful undead magically created by evil sorcerors. These mages realize their creation using special magical items which can absorb under the form of negative energy the nightmares of the people, and these nightmares form nightmare knights.

Fabio.