Dark Knight

"The pious Ishgardian clergy guide the flock, and the devout knights protect the weak. Yet even the holiest of men succumb to the darkest of temptations.
None dare to administer justice to these sacrosanct elite residing outside the reach of the law. Who, then, defends the feeble from the transgressions of those meant to guide and protect them?
A valiant few take up arms to defend the downtrodden, and not even the holy priests and knights can escape their judgment. Pariahs in their own land, they are known by many as “dark knights.”
These sentinels bear no shields declaring their allegiance. Instead, their greatswords act as beacons to guide the meek through darkness." — Game Description

Dark Knight, first officially announced during the 2014 London Fan Festival, is a Tank job that wields a Greatsword (2-handed sword) as its weapon. It wields not only a weapon but also the power of Darkness (magic-based tank). Unlike 2.0 jobs, Dark Knight will not have a base class and starts from level 30. It will come with the first expansion pack Heavensward in June 2015.

Unlike other tanks, Dark Knight will use MP instead of TP as its main resource. DK uses MP to cast a darkness buff that drapes the player with a darkness aura. Play style revolves around maintaining the aura, using it for defense, to buff yourself, or offense, to damage your enemies. It is a new style of tanking that will utilize Piety.

Dark Knight will have cross-class abilities from Gladiator and Marauder.

Requirements

Heavensward
Access to Ishgard, where Dark Knight's Guild is located.

Actions

Details of some of Dark Knight's abilities were announced during the Letter from the Producer LIVE Part XXI:

Darkside

Similar to a paladin's Sword Oath, this stance is more of an attack-based stance. You take on an aura-like effect known as Darkside, while this is in effect your MP will deplete gradually. While in this stance, you will not be able to receive MP healing support from party members. There are weapon skills which restores MP so it’ll be very important to make good use of those skills to manage MP.

Grit

This stance will be used when in the tank role. With this stance, it'll be easier to gain enmity. It will become important to switch between these modes when fighting and determining when you need to gain enmity and deal damage. Also, there are a lot of dark knight actions that start with “Dark.”

Living Dead

Similar to Holmgang, this is an all attack blocking action. Unlike other tank jobs, dark knight has an action where you jump towards the enemy, so it’ll be possible to use this first then follow-up with an area attack to gain enmity.