The Nightblade is a very strong and powerful DPS class. Nightblades can use stealth and quick damage attacks, or siphon the life of of an enemy and restore their own health and resources. With multiple burst abilities, DoTs, and an strong execute skill, they can be very strong in most aspects of play.
With this build there are 2 directions you can go. Vampire, or Standard. The posted build is standard, however the only change with the Vampire is your spammable. This would swap from Swallow Soul to Arterial Burst
Magicka Nightblade
DPS
Harvester
Beginner/Level
DPS
Mundus stone
The Shadow
Passives
Assasination
All
Shadow
All
Siphoning
All
Light Armor
All
Medium Armor
Situational depending on build. With Relequen, fill this out
Heavy Armor
Situational. For Magblade I don't find it useful outside of PVP
Destruction Staff
All
Dual Wield
All if using daggers
Undaunted
Command | Mettle
Dungeon/Trial
DPS
Potions:
Essence of Spell Power
Food:
Witchmother's Potent Brew
Warfare:
Fighting Finesse - 50
Deadly Aim - 50
Thamaturge - 50
Master-at-Arms - 50
Fitness:
Rejuvenation - 50
Siphoning Spells - 50
Boundless Vitality - 50
Spirit Mastery - 50
Craft:
Use whatever you like in this tree