there's a glitch which allows you to dupe consumable items, stones and souls
you need either evacuate or shard of archstone (can be bought from patches) equipped
make sure what you want to dupe is in your inventory, go and talk to baldwin and open the "buy items" menu, select something then when it asks how many you want walk away from him
when baldwin's menu closes either cast evacuate or use a shard of archstone, when the option asking "return to nexus" appears press start to close it then go and talk to thomas
deposit whatever you want to dupe then the evacuate/archstone shard animation should start and you'll appear at the other side of the nexus, if you check your inventory you should have 1 more of whatever item you deposited, now go over to thomas and he should have 102 of them