Need help with Mage Quest - Necromancer's Moon (Spoilers)

[Ferris Wheel]

I were recently orderd by an member of the mage guild to go to Dark Fissure were I were supposed to look for "Shade of the Revenants". So I went there. I saw an altar on the outside and some corpses, nothing out of the ordinary (when your expecting to meet Necromancers). So I go inside, there I find a bunch of necromancers/skelettons/zombies which I then proced to kill, after some time the whole place is empty on enemies and there are still no signs of the so called "Shade of the Revenants".

I then check the Walktrough on GB, there I read that I'm supposed to see an 'Red Light' when I first find the cave. So I figure that I should do something else for 3 days (game time) allowing the Necromancers to respawn and then go there again and approach the altar slowly. I do so but nothing happens, no necromancer goes outside and creates black soul gems on the altar.

I then sneak in with an invicible spell and check if there are any new things there or something that I might have missed the last time, nope, nothing new.

So, is the quest bugged? If so is there any way to 'walk around' the bug? Or have I done something wrong?

[Fer'or]

If I recall the correct quest then you (highlight to read)

Spoiler

have to wait, because at one night the red light you mentioned shines upwards from the altar and then you can find a black soul gem.

[Belthan]

spoiler

The altar only works one day of the week between dusk and midnight. It's a different day for each character (for mine it's Turdas). You just need check back nightly (or just wait at the altar in 24 hour increments) until you figure out what day it is. The "red light" you mention is a somewhat subtle lighting effect (kind of like a diffuse spotlight shining down on the altar from above) that occurs on the "special night", but it can be difficult to detect in cloudy or rainy weather.

[Ferris Wheel]

At last the weekend has arrived! I tried as you said, and waited and waited and waited and then at last the person showed up and I finished the quest. Thanks for the help!