Pallid Horror

Pallid Horrors are (elite) wights that periodically appeared during the Scourge Invasions. They are Neutral, so lower level characters can continue to go about the city without worrying that a high level elite undead will rain destruction upon them.

In Stormwind City, they are first spotted in the Cathedral of Light.

Drops
The notable thing about them is that when slain, a Faint Necrotic Crystal will appear at the body for a short time. (It stays somewhat longer than the body.) This crystal starts the quests