This is one of Lintking's and it's certainly interesting. Here's the pitch:

Ixi is a mischevious spirit who has long since forgotten where she really came from. She makes up a new story every time someone asks. Personally, she's very weak, but she is also hard to find and harder to hurt - almost more of a haunting melody on the battlefield than an identifiable shape. She makes an excellent spy.

Abilities: Caster (low), Frightening Tune, Invisibility, Inspire Courage
Perks: Ethereal, Undead, Evasion

Note: Ethereal is a bit strong for the Hero level, but Ixi has virtually no physical stats - she uses Frightening Tune and Inspire Courage to bolster the troops that she's with, and can cast some minor spells, but mostly, she's meant for world-map exploration - scouting and spying. If you can get some levels into her, though, her Caster could build up to something more exciting by the mid-game.

The idea is neat because you can see her working with living as well as the undead.