The enemies inside of the Parish are going to really test your skill, so we highly encourage you to take some time and level up. The knights inside of the Parish are tough, but they reward you with a slew of souls, making it a great place to grind for a bit. Be aware that these enemies can and will parry your attacks if you're not being observant. When you feel comfortable enough, proceed up the staircase just to the right of the elevator. Be cautious of the knight on the stairs.
On the second floor, try to pick off the large sorcerer from a distance. Fire arrows and Soul Arrows through the gaps in the columns to avoid is magic attacks. Funnel the zombies from the large room back into the narrow hallway to avoid being outnumbered. Once the room is clear, search the floor for items and souls. If you're having too much trouble, first clear the ground floor of all enemies, then take out the sorcerer with arrows before proceeding up the stairs. Use the columns for cover when it uses magic.
Break through a wooden door and ascend a staircase to find Knight Lautrec. This golden warrior is locked up inside of a prison cell. Free him, and he'll show up back at the Firelink Shrine next time you return. After you've explored the floor, ascend the two sets of ladders until you reach another white gate. On the other side lies the toughest boss challenge you've faced yet (When facing this boss, if you hack off the tail before vanquishing your foe you'll get a gargoyle axe).
Boss Fight: Bell Gargoyle
Walk halfway across the roof of the Parish to instigate this boss battle. At first the fight doesn't seem to tough. Keep your distance from the Gargoyle and fire off Soul Arrows when you have the opportunity. Time your rolls as soon as he swings his ax to avoid the attack altogether.
Just when it seems like you're going to cruise to an easy victory, a second Gargoyle appears from the other side of the roof. Although the odds are now stacked against you, both creatures should be at under 50% health. Concentrate your attack on one of them instead of chipping away at both. They are particularly weak against magic attacks, so Soul Arrows and Pyromancy are your best friends in this battle. Once you get one down, the second one should be a breeze.
With the creatures dead, walk to the base of the bell tower. There is an ominous looking vendor named Oswald who sells items are of great importance later. Remember his location once you get cursed. Climb the rest of the ladders and ring the first bell in triumph. Head back down to the bottom of the Parish and exit the church via the door directly across from the elevator. Head down the tree-lined path until you reach the ruins of a small chapel.
Head down the stairs of the chapel to find another bonfire. Head down yet another set of stairs to find blacksmith. If you have the souls to spare, use them to upgrade your weapons and armor. Sorcerers and other swift characters should take note that an upgraded pair of Leather Gloves are still worth equipping even near the endgame. Proceed into the next room to encounter another massive creature that is intent on destroying you.
Boss Fight: Titanite Demon
As a Sorcerer, this fight can be a breeze if you've already purchased the Heavy Soul Arrow from the vendor in the New Londo Ruins. Keep your distance, and the Demon will fall in just a few shots. The same tactic can work with regular Soul Arrows and Pyromancy. The Titanite Demon is deadly up close, so try to keep him just inside of your lock-on range. His ranged lightening attack is easy to dodge, so taking him down is just a matter of using your own ranged weapons to whittle down his health.
As a melee character, the fight is still fairly easy. The only thing worth noting here is that when you block his swing, he brings his tail around to hit a second time. So keep that shield up after the initial hit. (By the way this swing attack has a very long range) Just block both attacks, and circle or roll to his back and chip away at him. If you get low on health, roll away and dodge a lightning and then drink an estus. He is pretty slow between lightning bolts.
Press on after your victory to enter the Darkroot Garden.