Shimmering Wraith

These soulless energies are born where the Negative Energy Plane meets the Quasi-elemental Plane of Lightning. A shimmering wraith looks like a patch of shadow full of glittering sparks and is easy to overlook until it gathers into a ragged, man-sized shape just before it strikes. It neither speaks nor communicates.

Mindless, a shimmering wraith knows only one tactic: embrace its target. Each touch deals 1d6 electrical damage no matter what armor or clothing protects the victim, and up to three can grapple a man-sized creature at once. Strangely, every point it deals subtracts the same amount from its own hit points, until it fizzles out.

Any weapon can hit one, but a metal weapon conducts a jolt back to its wielder for 1 point each time it connects. In bright light, full daylight or continual light, its shadow becomes a second weapon: anyone the shadow touches takes 1d4 cold damage, armor or not, and the DM must judge where the light falls and the shadow lies.

Cold and electricity do not harm it. It cannot be turned and dispel magic does not remove it, but banishment sends it back to the Inner Planes. Faced with wards like shield, protection from evil, wall of force or wall of iron, or with physical barriers, it turns ethereal, drifts through at half speed, solidifies and attacks again.

They seem to lack real awareness yet pick out and pursue particular targets, because they are the product of an elemental's curse. A bound elemental cannot curse its master or loose these wraiths on a former summoner, but one that breaks free on the Prime Material may curse anyone who foiled its plans or tried and failed to bind it.

A day after the curse, a single wraith arrives and attacks. It is easily destroyed, but the next day two come. Every day after, the number is multiplied by itself to give the next day's count, until the victim is dead. The curse ends only when the elemental is found and bound or destroyed, or, if it has gone home to the Inner Planes, summoned and bound, which forces it to lift the curse. It must then be appeased or banished to stop it cursing again.

Some mages suspect these wraiths could charge wands of lightning and similar devices, but since they always fight to the death and vanish when beaten, the idea remains untested.