Continue your journey with Prima's Dark Souls 2 Guide and Walkthrough!
Take out the guards that drop down when you first enter Sinner's Rise, then head through the doorway in the corner. To the right is a ladder that leads to a bonfire. To the left is a staircase that leads down to a room with several archers. If you're feeling confident, take out the archers first, otherwise climb up the ladder to the right, light the bonfire, climb back down and engage the archers.
If you climb the ladder, head into the doorway on the right (before you reach the bonfire), to find a Large Soul of a Lost Undead. Be careful not to fall off when you pick it up, since the item sits on a small ledge. Once you have the item and light the bonfire, climb back down the ladder and follow the path around the corner, past the room with the archers, to find a Human Effigy item at the end.
Inside the room with the archers, step onto the lift in the middle to ride it down to the bottom. You can jump off on the floor just above the bottom level to find five Lacerating Knives. If you do this on the way back up, drop down to the bottom level while being careful not to fall into the water, then use the lever to summon the lift again if need be.
Your next objective is to head down the ramp and into the water below. There's a large enemy to the left, which can be easily bested if you lure it back into the room with the lift, then get its attention just as you take the lift back up to the floor above. With proper timing, the monster will fall into the water below, dying without putting up a fight. If you wish to fight the enemy, it's best to use a ranged weapon or bait it into attacking, then dodge its attack and counter while it's recovering.
To the far right, just behind where the enemy was, pick up the Sublime Bone Dust. Head over to the opposite side of the area to find another enemy. Use the same tactic of luring it into the room with the lift, then tricking it into falling in the water as you take the lift to safety. Behind the enemy is a Large Soul of a Nameless Soldier in the corner.
There's another large beast on the other side of the area. You need to take it out before you move on to avoid having to face several enemies at once. Just ahead and to the right is one of the zombie-like enemies that falls near you to inflict damage. Take it out, then head up the stairs to the right. Ignore the two cells, as there's nothing in them, and take out the sleeping enemy at the end of the path. Head around to the opposite side and take out the other sleeping enemy, once again ignoring the cells.
Take the stairs back down to the water and continue down the watery path. The cell on the right in this lower section has a single enemy, while the cell on the left has two enemies. Move toward the opening of the cell on the right to get the enemy's attention, then back up to avoid getting the attention of the enemies in the other cell.
Defeat the enemy, then move into the other cell only far enough to get the first enemy's attention. Move away from the cell and take down the first enemy as quickly as possible. You want it dead before the second enemy emerges from the cell.
With all of the enemies down, move forward to find the final enemy in the last cell on the right. Pick up the Soul of a Proud Knight and Pharros' Lockstone in the last cell on the left, then pull the lever at the end to open the gate ahead. The mist ahead leads to the boss battle against the Lost Sinner, but before you enter, head to the left of the mist (not up the stairs) to find a Radient Lifegem in the corner.