Dark Souls 2: Belfry Gargoyles Guide
How to get to Belfry Luna
From the servants quarters bonfire in the Lost Bastille you want to take the ladder that is directly in front of you, it will lead you down into a dark room. In the dark room is a dog that is guarding a body, and a Pharros contraption. The dog will be to your left, quickly kill it and use a Pharros Lockstone in the contraption. This will show a hidden doorway towards Belfry Luna.
If you do not want to get invaded by other players, then now is the time to play in offline mode, otherwise be ready for a few fights.
Upon entering Belfry Luna there is a dwarf NPC, exhaust all of his speech options and he will ask if you want to join the Belfry Covenant (you don't have to if you do not wish to, this covenant is strictly for player vs player). Head up the stairs to meet your first dwarf enemy. There are a few holes in the flooring so be wary, one of these holes (the one closest to the first enemy) will let you drop down into a hidden room.
After defeating the first enemy, head up the second flight of stairs to meet two more dwarf spirits. You'll notice after killing them that the mist door blocked off by a cage. Take the ladder up to the top of the bell tower, but be careful there are four more dwarf spirits waiting for you. (NG+ has a 5th red spirit dwarf) Quickly run behind the wall in front of the ladder and stay in that corner, doing so will allow you to pick off the first two spirits. Kill the two (or three) remaining spirits, grab the chest and then pull the lever. The giant bell above you will ring, letting you know that the cage in front of the mist door is now removed. Head back down the ladder and enter the mist door for the boss fight.
The Belfry Gargoyles:
This boss fight had me white-knuckled, and spouting profanities because of how annoying it is. Upon entering through the mist you will notice that you are on a rooftop, with a lot of gargoyle statues. Two of these statues will immediately come to life, pick one and begin wailing on it. You are always fighting 2 - 3 gargoyles at a time during this fight, so it is ideal to kill one as fast as possible. Fighting two gargoyles is a lot easier than fighting three, and yes a third and fourth gargoyle will join the fight if you are not eliminating them fast enough.
Four to six gargoyles will appear during the fight, during my first and second play through I have only met four. The longer this fight lasts, the harder it is going to become.
The general idea for this fight is to focus on one until it is dead. If a gargoyle is below 50% health, it will take a more ranged approach and begin to breathe fire. If you have a shield with 100% damage reduction this fight is a lot easier, if not then you best freshen up your dodging technique. If you need to switch to a two-handed weapon to deal more damage, then please do so. I however found that my +10 Fire Morning Star was more than enough to get the job done, without having to drop my shield.
The gargoyles will do a lot of basic attacks, like a swing or a tail sweep. Occasionally they will jump up into the air and do one of two attacks: A diving slash attack (avoid / block if possible, this one hurts) or they will jump behind you and back stab you. The only way to block the back stab is if you have that particular gargoyle targeted, if not then prepare to take a doozy of a hit. (Trying to dodge this is simply impossible for me, no matter how many times I try, I get wrecked with it.)
Very rarely will a gargoyle use its lightning storm attack, but if it does your best bet is to start running. I have only met this attack once and I just outran any and all damage from it.
Their weakness is lightning, so if you got lightning resin now is the time to use it.
Killing the Belfry Gargoyles rewards you with 25,000 souls (50,000 in NG+) and the Belfry Gargoyle Soul. The soul can be traded with Straid for the Gargoyle Bident, or consumed for 6,000 souls.
Finally, The Key!
After defeating the gargoyles, head across the rooftop where you will see a bonfire. Light the bonfire and continue moving forward, you should come to a walkway that has a ladder leading down. There is about five or six dogs waiting for you at the bottom of the ladder, slide down quickly so they do not bunch up on top of you. You want to run towards the top of the stairs and pick them off one by one, just be wary of the red spirit that invades your game. He will spawn a few moments after getting off the ladder.
If you wish to use range attacks during this, you can get the dogs attention by sliding down to the bottom and then climbing back up. You can target them from the top of the ladder. The invader will not follow you up, but be careful of his spear, his attacks are quick but he is fairly slow-moving. This part is a real pain, but remember to stay calm and take care of those dogs first. If you are getting overwhelmed then run up the stairs, you can also jump down in front of the small archway if the top of the stairs become too heated. You will take a little fall damage, but its better than dying.
After the skirmish you can finally loot some bodies. The bottom one will have the Bastille Key and the top will have an Enchanted Falchion. Best of luck!