https://www.pcgamer.com/bungie-details-destiny-2-exotic-masterworks-and-more-changes/

Following the big Destiny 2: Warmind reveal from earlier this week, today's This Week At Bungie blog post delves into one of the big changes coming to the game with the start of season 3 in May: The quest to make Exotics "feel more exotic." A big part of making that happen will come in the form of Exotic Masterworks, which senior investment designer Mark Uyeda said will "create new in-game goals for hobbyist players and reinforce specific activities with these long tail pursuits." 

There will be a specific Exotic Masterwork upgrade for each Exotic weapon in the game, which will be available via a process that begins with the discovery of an Exotic Masterwork Catalyst. Exotic weapon descriptions will provide a hint about what activities grant the catalyst for each weapon: Some are guaranteed to drop "after a certain amount of engagement," while others will appear at random.