Which stone would be more beneficiary for a nightblade? The mage, the thief or the warrior. I am a dark elf hybrid one-handed destruction / alteration / illusion nightblade assassin going into the dark brotherhood.

EDIT: Nightblade

You could always get the Lover Stone 15% to all.

Mage. You still should be focusing one magic if you are a Spellsword. That's also what was the focus of the Oblivion Spellsword class.