Doors of Pharros

A small area, where most of the Pharros contraptions don't lead to treasures. Don't waste your Pharros' Lockstones on all contraptions because at this point in the game Lockstones aren't easy to farm. Later on when you reach Dragon Aerie you would be able to easily farm Pharros' Lockstones. For the moment, you can farm Lockstones from the two rats in this area.

31. Doors of Pharros, Dark Souls II: SotFS

As a member of the Rat King covenant, enemies in this area would be passive toward you and you can't hit them. Furthermore, while a member of the covenant, you wouldn't be invaded by an NPC. Ensure you have defeated Royal Rat Vanguard, have a Rat Tail in your inventory, and talk to the Rat King at the Grave of Saints to join his covenant.

Light the Gyrm's Respite bonfire and the Ordeal's End bonfire. You can find Gavlan at this area, where he would remain for the rest of the game. Take this opportunity to stock up on Poison Arrows. Spend at least 16,000 souls in his shop and he would gift you the Gyrm Greataxe. Whenever you need to sell items, warp to the Gyrm's Respite bonfire and visit Gavlan.

Royal Rat Authority

This is a gank boss. You will be harassed by four rats that can inflict petrification. At the same time, you must deal with the boss. The boss is weak against fire. Use any weapon you are comfortable with. Traverse the fog wall, stay where you are, and use the Dragonrider Bow and Iron Arrows to dispatch of one or more rats before the mob reaches you.

Defeat the boss, make your way outside the arena, and you will meet the Rat King the second time. Exhaust his dialogue and purchase anything you need. Proceed to Brightstone Cove Tseldora and light the Royal Army Campsite bonfire.