Mora's Soul Trap

A spell given to you by the daedric glob (he is technically a prince but looks more like a blob with claws)Mora. You must use the soul trap on one member of each race and kill them. The souls will be transported to his special stone that he gives you.

Bugs
On some 360 versions of the game, it takes the spell several times to take effect, use it multiple times until you see the dialog "This person is already affected by Mora's Soul Trap". The attack does not spark a battle so you can cast it as many times as necessary before attacking.