The Nightblade is a playable class in the Elder Scrolls Online MMO, designed to use the night and shadows to sneak around and perform sudden strikes for high damage to unsuspecting enemies. It should go without saying that a hidden attack is never expected, which is why delivering an attack from stealth to an unsuspecting enemy will cause higher damage. Nightblades are friends of the nighttime and are very familiar with using magic in order to weaken their enemies. The best choice of weapon for this class are light weapons, such as small swords and daggers.
While the Nightblade works best with light weapons, the best armor for this class is medium armor. This is because it will provide enough protection while keeping movements quiet; in fact, it is nearly impossible to detect a good Nightblade who is donning a set of medium armor. Keep in mind that this kind of armor also provides a bonus to your stamina pool, which is the major resource pool for a Nightblade. Similarly, heavy armor is a bad choice if you are looking to play sneaky since it will not provide any bonus to your stamina or sneak skills, though it does increase your health and damage resistance. Above all, being a Nightblade will not be easy, but you do get the versatility in how you want to play.
The Nightblade can train in three different trees: Assassination, Shadow or Siphoning.
As the name suggests, this tree is designed for Nightblades who wish to sneak around and deliver powerful attacks to assassinate enemies with one go. The skills are as follows:
Assassin's Blade: An active ability that deals damage, with more damage dealt to those with low health.
Teleport Strike: This active ability causes you to transport to your target, stunning them and dealing direct damage.
Blur: This active ability lets you debuff your enemy by lowering his accuracy.
Mark Target: This active ability lets you put a mark on a target with high health, which causes that target to take extra damage; you will also be healed if you kill this target.
Haste: The final active ability, this briefly increases how fast you can attack with your weapon.
Death Stroke: The ultimate ability of this tree will deal damage to the target and reduce how much healing they can receive.
Appropriately named, this tree lets you turn invisible briefly, remaining active even when dealing damage. The skills are as follows:
Shadow Cloak: Grants invisibility briefly.
Veiled Strike: This active attack will deal more damage and also stun enemies, but it requires stealth.
Summon Shade: This will summon a shade creature to attack enemies.
Path of Darkness: This will damage enemies directly in front of you and increase your speed while on this path.
Aspect of Terror: Enemies nearby will gain Fear.
Consuming Darkness: This ultimate ability buffs you with an increased dodge chance.
The final tree, this focuses on dark magic as you siphon health from your opponents. The skills are as follows:
Strife: This places a DoT on a target that will heal you.
Agony: This will place a DoT and a stun on an enemy, but any other damage will drop the effect.
Cripple: This puts a DoT on an enemy and slows him, granting an equal speed bonus to your character.
Siphoning Strikes: In exchange for self weapon damage, you can gain some stamina and magicka back with damage.
Drain Power: This causes nearby enemies to drop attack power, granting it to you instead.
Soul Shred: This ultimate ability deals major area damage and stuns enemies.
More detailes about the Nightblade could be seen in this site