Mullered Moose wrote:Soul arrows? don't think I've come across those yet, yeah I'm sure I've picked that up don't know where the door it is used for is though.
Did you grab the sorcerer's catalyst from the undead asylum? If not you can get back there via the crows nest.
From firelink shrine bonfire go down the stairs and use the lift down to New Londo ruins. Don't go left into New Londo instead hug the right wall and you'll come to an undead lying down. Follow the stairs down to left for a smith who sells the heavy soul arrow.
The basement key door is at the opposite end of the bridge where the red dragon is. It takes you down to the lower undead burg and connects to a door close to the undead burg bonfire and the firelink shrine waterway. On that waterway you'll find a woman who sells resins for imbuing your weapons and mosses to counter poisons. If you've done the bell tower gargoyle there's a bloke in the belltower whom you can purchase a poisonbite ring from to up your poison resistance.