Silhouette

If one wishes to make a deal to the Silhouette the person the prospective warlock most loves must be sacrificed.  After that the Silhouette takes that person as their vessel.  The Silhouette then strikes a deal with the warlock and then leaves.  Until that goal is achieved the Silhouette is active, roaming the earth and taking innocent people into its thrall.  Once the pact is fulfilled the Silhouette and its thrall must return to the infernal realm and the warlock looses their power.  If the warlock dies the pact will never be fulfilled and the Silhouette will remain in the world until their vessel is killed

Shadowy form

As a result of your pact the your skin/hair/feathers etc... is stained black.  As a result of this you gain +5 to stealth in dark areas and -5 to stealth in light areas

Cloak of shadows

Once per day you may touch any number of creatures staining them black for ten minutes.  During the duration of this effect they gain a +5 to stealth while in dark areas and -5 to stealth in light areas.

Eyes in the darkness

Your sight is unimpeded by natural darkness or the darkness spell.

Shaded step

When in complete darkness your movement speed is doubled.