Wraiths

Wraiths are a moderate to high-level form of incorporeal undead. While the word "wraith" may be invoked with relative ease across Faerûn, knowledge of what exactly a wraith is and what it's capable of is rare.
Wraiths are capable of flight, and can pass through solid matter. They are fast, hardy, hit hard, and drain the vitality from their victims. They are also capable of creating specters from nearby fresh corpses, making them a particularly dangerous foe to fight as a group if you're lacking resurrection magic.
However, wraiths are vulnerable to sunlight, preferring to fight in the shadows. They are also vulnerable to attacks with silvered weapons.