The six exotic weapons can be unlocked by examining lore nodes found throughout the Hunting Grounds, with each one unlocking a quest to forge a specific item. The new area is called Conundrum Rocks, and it’s a level 10-13 instance of Paradox Breaks, with its guaranteed Behemoth being Valomyr.
As for the new armor — excuse me, armour — it’s the Timeweave set, and its schematic can be obtained from lore nodes on the Paradox Breaks. It brings Overpower, Predator, and Catalyst perks to today’s stylish Slayer.
Update 1.6.5 also makes a number of tweaks to various game elements, modifying eight exotic weapons as well as nerfing a specific combo with all sword weapons. You can get all the details on the bug fixes, UI changes, and quality-of-life improvements on the Dauntless site.