I've read you need to run Nightfalls to get the catalyst. Nightfalls have been removed by Bungie. This is one of the few Exotic heavy weapons that you can use that are ARC to complete Grandmaster Conquests for the progress of your Journey which required AVANT-GUARD only. Do people at Bungie no longer think? Why are all the Exotics not available for us to use as we wish in our Journey? We grinded for them. And you restrict and then actually prevent getting components to the weapons you restrict. Unbelievable.