Out of the ten available classes in Lords of The Fallen, the Dark Crusader is one of the few that are not unlocked as you start the game, unless you received it as a reward early. Boasting high defense combined with the ability to cast Radiant spells, this can be a powerful archetype for those who favor an aggressive approach. The excellent starting gear also makes this class an appealing choice at the start of a new adventure.
The Dark Crusader specializes in Strength, Endurance, and Vitality, reflecting its strong melee combat similar to a Motivity build in Lies of P, another title similar to the Dark Souls series. However, this elite military Paladin also wields magic from the Church of Orian Radiance, using a Radiantburst Parchment as ammo. When you equip your Throwing Hand, you are able to throw these exploding papers at enemies as ranged attacks in Lords of The Fallen.

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How to Get the Dark Crusader Class Early in Lords of The Fallen
Anyone who purchased the Deluxe Edition of Lords of The Fallen get the Dark Crusader class instantly, while others have to complete the quests surrounding the character Issac. Starting with this class gives you Paladin Issac's Sword, as well as the Paladin armor set. You also receive a Paladin's Pendant as part of your starting equipment, which increases your Strength and Endurance attributes.
For those who do not wish to buy the upgraded edition of Lords of The Fallen, they'll have to play through the game to find the body of Issac first. You need to collect the Flayed Skin item past the broken bridge to the right of where you fought the Lightreaper boss. In the Umbral, you can then see Issac's corpse past a blocked path that only unlocks when you examine Stigmas tied to Issac's mission from when he was a Dark Crusader.

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There are four Stigmas to investigate around Lower Calrath, the Fief of the Chill Curse, and the Path of Devotion. When you go through all of these, you can challenge Issac's spirit in an arena that opens up in the Path of Devotion. Defeating the former Paladin here in Lords of The Fallen grants you the Umbral-Tinged Flayed Skin, an item that can unlock the path you saw earlier in the Abandoned Redscope.
Doing this grants you the Paladin armor set, Issac's Sword, and a new item called Paladin Issac's Rosary, symbolizing your connection to the fallen warrior. From now on, you'll have the Dark Crusader class unlocked in Lords of The Fallen for you to use early, along with a new summon of Issac to use against the Lightreaper later in the game.