The Silhouette looks like the shadow of a medium size human with a tail, but it is utterly black, like a void, regardless of lighting conditions. It can turn itself on edge to become invisible to victims viewing it straight on, or from up to 15-degrees left or right. When the Silhouette is so aligned, the ability to see invisible objects does not reveal it, nor does infravision or ultravision.

The Silhouette’s humanoid-shaped body actually has a thickness that extends out of the PM plane into the ethereal. On the ethereal plane it appears as a featureless shape. It does not attract the attention of standard ethereal monsters, although it can be attacked with a to-hit penalty of -2 on that plane.

The Silhouette is of moderate intelligence and will retreat from a fight that is going badly for it. It can innately detect precious metals, gems and magic auras at up to 120 feet, and will stalk creatures carrying such treasure, waiting for the best opportunity to attack. When it catches the “scent” of a party in this way it will identify the person carrying the most valuable or most magical items and will concentrate on that person first.

The Silhouette can move at twice normal human speed when it wants to, usually when it attacks or flees. A typical attack strategy against a party is to rush in, attack one person, and rush away until the entire party is within the 10-degree wedge behind it, so it can effectively vanish. Often it will then seek cover and lurk, to attack again at the next opportunity. During movement a Silhouette makes very little noise. When moving at normal human speed it can Move Silently as a level 10 Thief.

A silhouette can attack with a whip-like pseudopod which it extrudes at will from each hand. Each whip does 1d8 damage + 1d6 cold damage. A whip attack that misses by 2 or less still inflicts 1-3 points cold damage from proximity. Each hand can attack a different target in the same round. The silhouette also has a tail sting that does 1d4 damage + poison (save or die). The silhouette greatly prefers head-on attacks on single victims, or on parties marching in single file. In such attacks it automatically gets initiative. Victims lose any defensive Dex bonus.

While making a head-on attack the Silhouette is visible as a ropy black shape in the air, as it twists its body to strike. Opponents viewing straight-on can counterattack at -2 during that round. Opponents outside the 15-degree wedges see the Silhouette as a black humanoid shape and can attack normally. There is essentially no way to back-attack a Silhouette.

Special Attack: Absorption
When any object makes contact with a Silhouette, the creature may attempt to Absorb it. In this case the object must roll a saving throw vs Magic or be absorbed into the creature’s body. Magical objects save at +1, with an additional plus for each plus the object has (e.g. a +2 sword would save at +3). A creature holding an object so absorbed must make a successful DEX roll to drop the object. creatures who fail are absorbed at the same time. Absorbed objects and creatures are not damaged; they are merely trapped in the ethereal cavity within the Silhouette, which is somewhat like a Bag of Holding with no opening. Creatures that require oxygen must find a way to escape or they will suffocate. The cavity contains enough air to keep a single human-size creature alive for ten rounds, two for five rounds, etc.

Special Attack: Embrace of the Void
When a Silhouette scores hits with both whips in the same round on a single victim, it momentarily wraps the victim in a deadly embrace that is similar to the touch of a Wight. The victim loses one life level and is Stunned for 1d4 rounds. The victim’s hit points for the lost level are immediately absorbed by the Silhouette, which will either release the victim and attack another or continue to attack the same victim, depending on the situation. If the creature scores critical hits with both whips, the victim loses all remaining HP to the Silhouette and is instantly sucked into the Void, along with all of his or her possessions. There is no saving throw, and only a very high-level power such as divine intervention or a full Wish can bring someone back.

The Silhouette’s whole existence is driven by maniacal greed. It craves gems, precious metals and magic items, which it hoards inside its own body through Absorption. The body of a dead Silhouette, which can be cut open like any other creature, will typically contain a highly varied assortment of objects.

Because of the high treasure potential this creature should be tough - I would say 11-14 HD with 90% magic resistance. This will enable it to survive long enough in combat against a powerful party so it will have a slight chance of using its level drain ability. Accordingly it should have pretty pretty massive XP.