If you haven't purchased the expanded edition of the game, but you really want to play as the Dark Crusader (Dark Crusade), then you can get it as a reward for completing the mission "The Paladin's Request". In this guide, you will learn how to complete the quest.

Where to find and how to complete the mission

The quest can be started immediately after completing the training in the location Defiled Sepulchre. Run down the hill and near the arena where you defeated the Lightreaper, turn right. 

Approach the edge and pick up the Flayed Skin. By doing this, you will activate the start of the quest. 

The mission consists of a series of explorations into the past of Paladin Isaac using Stigmas (echoes of the past in the shadow world). We need to study the stigmas in the following locations: Lower Calrath, Fief of the Chill Curse, the arena where we fought with Lightreaper, and Path of Devotion. All these locations are part of the storyline, you won't miss them.

The first stigma is located near the burning city, which you will access after exploring Fitzroy's Gorge. 

From the location of Vestige of Sebastian, go down the stairs and turn right before the broken bridge. Enter the shadow world and cross the bridge. 

This way, you will find the first stigma and receive the Wooden Dark Crusader Cross.

The second and third stigmas are located in the Fief of the Chill Curse. To access them, you will need to take a key from Andreas of Ebb. 

One stigma is located next to the Vestige of Svornil. In this location, you will see a praying dark crusader. After defeating the Hollow Crow, which is the area boss, you will open the path to the third stigma. 

From the boss battle arena, go to the place with the lit torch and go down the stairs. 

As soon as you reach the broken bridge, switch back to the shadow world and climb the hill. 

The stigma we need is located to the right of the riverbed.

The last stigma is located in the Path of Devotion area.

To get into this region, you need to use the Pilgrim's Perch Key, which you can buy from Stomund.

Find the Vestige of Blind Agatha and head into the caves. There you'll find a door that can be unlocked with the purchased key.

Enter inside, and from the Vestige of Dieter, follow the path to the left until you reach a tall cliff. Switch to the shadow world and find the final stigma.

After finding all the stigmas, the path to the Paladin's Burden boss will open. Head down the road. Switch to the shadow world and turn left to the bone bridge.

Go across it, and you will encounter the boss. Examine the stigma and face the paladin.

For your victory, you will receive the following items: one Umbral-Tinned Flayed Skin, eight Umbral Scourings, and one Vestige Seed.

Return to the Vestige of Ranik at the starting point of the mission and use the items acquired from the boss battle to obtain: Paladin Isaac's Sword, Paladin's Gauntlets, Armour, Helm, and Leggings.

The finale of the quest involves summoning the phantom of Paladin Isaac and defeating the Lightreaper. The Dark Crusader class will be unlocked.