The catalyst drops from a secret quest you have to do in the raid with Necrochasm equipped (stand on a few plates to activate, kill knights with swords). After you get the catalyst you have to get 15 more oversoul essence to complete it. So you won't have to do the final step, but you just need to do the puzzle in the raid to acquire it.
[quote]The catalyst drops from a secret quest you have to do in the raid with Necrochasm equipped (stand on a few plates to activate, kill knights with swords). After you get the catalyst you have to get 15 more oversoul essence to complete it. So you won't have to do the final step, but you just need to do the puzzle in the raid to acquire it.[/quote]
Thanks!