I am starting a new character and want to role a Nightblade. I have never played as one before but wnated to know a couple of things.

• How were Nightblades used in Tamriel?
  
• What services did they offer?
  
• What is the best race for one?
  
• Based on answers form 1 and 2, what questlines should be my dominent ones?

Thank youin advance for your responses.