Where can I find a second copy of Great Soul Arrow?

I'd like to get a second copy of Great Soul Arrow in order to assign it to two attunement slots, but Griggs, the first spell merchant in Firelink Shrine, only seems to have one copy.

How do I find a second?

Solution 1:

Big Hat Logan sells a copy as well, and is initially found in a cage within Sen's Fortress. After getting past the second platform containing swinging blade traps, you'll quickly come across a sleeping snake guard leaning against a wall. Big Hat Logan is located in a room hidden behind this wall, only accessible by breaking the wall.

To break the wall you need to redirect the metal balls you see throughout the fortress. The mechanism to do this is located after the second room with the metal balls coming at you. You want to redirect the mechanism to the hallway opposite the exit which will simply drop the balls off the game map.

In order to unlock the cage he is located in you need one of the following:

• Master Key: This is a possible starting gift, and the Thief class will always start with it.
• Cage Key: This is located further on in the fortress, shortly before fighting the boss. On your way to the boss you'll notice that part of the bridge is broken. If you jump over this (dash + action button) you'll find yourself in a tower with a merchant, and at the bottom of the tower you'll find the cage key.

After you free him from the cage he'll return to Firelink Shrine, where he'll start selling spells. He'll stay there until you put the Lordvessel on the Firelink Altar, at which point he'll relocate to The Duke's Archives. Make you sure buy his copy of Great Soul Arrow before he moves, since he won't become a merchant again until after you've gone through a large portion of The Duke's Archives.