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I purchased all his spells he went mad and when I went to seaths boss arena he was not there and the chest apeard in his place.Wtf happened?
You have to reload the instance without progressing. Easiest way to do this is by reloading the game.
If you don't save him at Sen's Fortress, he won't be in the prison at the duke's Archives
You must let him out of his cell, reload, meet him at the side room next to the room with the stairs that go down and to the yard before the crystal cave, buy everything before you kill seath. After you kill seath light fire but don't sit, homebone to the last fire (mine was the one closest to Logan that hangs over the yard. Go directly to Logan, he will say all sorts of crazy things he doesn't know you. Leave, I went to seaths room and grabbed the big magic ember and the hero soul. Then I went and warped to firelink because he wouldn't leave where he was sitting and so I messed around a minute and got the trophy for magic weapon, warped back went back to downstairs room, he was not sitting there anymore, went up to seaths room he was standing naked in his hat. Had all silence and fog gear merc'd him before he could get a spell off, he dropped dragon breath, his hat, and tin crystallization catalyst, but not his underwear. I still don't have his outfit just his hat. Will reset and see if it pops up in seath's room. Did this in the last 30 minutes no issues whatsoever. I did all his previous steps obviously or he wouldn't have been locked up to start with. -tearlach2
After reloading, again, a 2nd new chest was where he sat and sold stuff with his clothes and Logan's catalyst in it.
So if I didn't free him from Sens Fortress before getting the Lordvessel where would he be?
Big fat Logan