Post-Boss Exploration
The Soldier Key allows you to open several previously locked doors in this location. The first one is located on the top of the Cardinal Tower bonfire. Loot the chest inside to get a Small Leather Shield and Repair Powder. Defeat the guard sitting on the wall then loot the corpse behind the wagon to get a Hand Axe and a Radiant Lifegem. Open the door to find the lone chest containing an Estus Flask Shard and a Small White Sign Soapstone. From there, peek through the hole to find a hanging corpse on the tree root. Loot it to get a Diving Blessing.
The locked door across the burning pit with the salamander, right under the Cardinal Tower bonfire. After opening the door, go straight and loot the chest there to get a Ring of Restoration and Torch x3. Equip this ring immediately since it will gradually recover your HP. If you head outside, there's a massive black door that will tell you to "produce the symbol of the King". Just take note of this place and leave for now.
Another locked door is found in the next room under the Cardinal Tower bonfire, right before you reach the flooded open area with a tunnel. Go downstairs and take out the undead sitting to your immediate left. This is a long corridor filled with various enemies. In the corridor to the left lies a corpse containing x3 Black Firebomb and a Homeward Bone. At the end of the corridor you'll find another corpse containing a Torch.
Open the door which leads to an area outside. Enter the next door and take out the mauler there. Climb the ladder to find a couple more maulers. Defeat them then loot the corpse of nearby to get a Soul of a Nameless Soldier and x3 Cracked Red Eye Orb.
Climb back down using the ladder where you came from and continue along the corridor. Take out the undead there and loot the corpse to get a Bast*rd Sword. Exit the room and defeat the mauler standing by the gate then loot the corpse behind him a Green Blossom and Amber Herb.
Continue through the ruins and head to the next building. Enter the large opening and you should be able to light up a new bonfire (Soldier's Rest). Go up the platform in the corner to find a chest containing several items: Large Soul of a Proud Knight, Hunter's Hat, Leather Armor, Leather Gloves, and Leather Boots. That's all there is in this area so fast-travel using the bonfire to leave the area.
The next locked door that can be opened by the Soldier Key is located in the same corridor where a giant stone blade was found. You can access it easily by fast-traveling to the Cardinal Tower bonfire and go to the left past the lift.
After opening the door, continue upstairs. Beware of the shielded spearman and pikeman. Continue upstairs and you'll find a misty door. Before entering it, take the stairs to the right and loot the corpse for a Soul of a Nameless Soldier and Lifegem x3. The enemy behind the misty door is The Pursuer himself. Before fighting him, make sure that you've used your souls already, especially if you stocked quite a bit after defeating The Last Giant. If you killed while fighting The Pursuer, you don't have any way of retrieving your dropped souls permanently until you defeat him.
Boss: The Pursuer
He is especially challenging because of his speed and his weapon's wide range so when fighting him, you have to keep on the defensive and attack him whenever there's an opening. This battle will be easier once you have enough stamina to evade several times and land some attacks. Don't bother blocking his attacks if your character is not efficient in handling shields since it will consume a lot of stamina. When you see him readying for a charge, move towards him and evade to his right side (to the left of your character). This will ensure that you'll evade his upward slash and attack him from behind.
There are ballistas here that can fatally wound him and allow you for a quick kill but lining it up and timing your fire can be challenging, not to mention that the ballistas can be destroyed. Your best hope is to evade and attack as soon as his combos stop. When you have a stronger weapon and higher stats, you should be able to defeat him and survive his attacks.
If you examine the nest in the area behind The Pursuer, you'll be taken by a bird to Lost Bastille. Fortunately, there's a bonfire from where you'll land that you can use to travel back if you selected it by mistake.
In the same area, carefully drop down the broken part of the wall to find a corpse. Loot it to find a Drangleic Sword, Drangleic Shield and a Drangleic armor set. The Drangleic Shield provides a 100% damage reduction rate, perfect for some upcoming boss battles. Its low STR requirement makes it a very good shield for almost any melee-based class early on.
this is useful for getting past the pursuer.