One of the major features coming with patch 9.2 Eternity's End is the chance for PvP and Mythic+ players to gain the opportunity to earn the new Tier Sets without the need of stepping inside of the raid.
This will also help players who raid obtain set pieces that they might have not had dropped inside the raid yet, obtain those items that fill their 4-sets, and do not cross over with legendary slots.
A new currency is being introduced called Cosmic Flux, which will also be used to upgrade legendaries in Eternity's End, and then can be used in a new system in Zereth Mortis called the Creation Catalyst once players fully unlock the secrets of the first ones.
This new currency can be earned by completing many types of content throughout the shadowlands including defeating raid bosses, PvP, Mythic+, Torghast, and World quests. Blizzard says they gained inspiration for the currency from 8.3's Echoes of Nyalotha.
Details Released On How Tier Sets For Mythic+ And PvP Players Are Obtained In Patch 9.2 Eternity's End
To give a simple example, if a player loots a 265 Mythic+ chest piece they can use the Creation Catalyst and Cosmic Flux to turn that piece into a 265 Tier Set of their class.
While this system won't be around at launch as players will need to unlock the reputation in Zereth Mortis, players will still be able to save any item they do loot prior to unlocking the Creation Catalyst and can begin saving Cosmic Flux to use.
Tier sets bring back 2 and 4 set bonuses unique to each specialization in the game and can be obtained by a mixture of Helms, Shoulders, Chests, Quantlets, and Leggings.