Shadowlands Season 4 Fated Raid Overview
In Season 4 of Shadowlands, there are no new raids - Instead, we will return to the 3 Shadowlands Raids: Castle Nathria, Sanctum of Domination and Sepulcher of the First Ones. These raids will return offering a higher level of difficulty with better loot, as well as a new raid affix that will further increase the difficulty of said raids.
Special Fated Raid Rewards in Shadowlands Season 4
Being a special season, there are three special rewards from completing all raids in Fated difficulties. These rewards come from the three meta achievements for completing all three Shadowlands raids while they're Fated raids.
Normal Fated Raids: Jigglesworth Sr. Mount
Fates of the Shadowlands Raids: Complete all three Fated raids on Normal difficulty or higher in Shadowlands Season 4. Mount Reward: Jigglesworth Sr.
Heroic Fated Raids: Hero of Fate Title
Heroic: Fates of the Shadowlands Raids: Complete all three Fated raids on Heroic difficulty or higher in Shadowlands Season 4. Title Reward: %s, Hero of Fate
Shadowlands Season 4 Fated Raid Vendors

As Fated raids are on a three-week rotation, you might experience increased bad luck when aiming for specific items. To counteract this, Blizzard is experimenting with specific loot vendors, that will sell Trinkets and Weapons purchasable with  Puzzling Cartel Dinar. In addition to this, you will be able to upgrade Fated items via  Cosmic Creation Impetus and Sacred Creation Impetus. How the system works:

There's a 3-part questline in Shadowlands Season 4.
The questline involves killing a certain amount of bosses. Crossing Fate: Defeat 30 different Fated raid bosses, Rewards: Puzzling Cartel Dinar. but players clearing 10 Fated bosses per week should complete the 3 quests in 3 weeks.
For players joining later into Season 4, the quest requirements will be reduced over time.
The Rewards are a currency in which you can buy the exact piece of Normal raid gear that you want ( Puzzling Cartel Dinar). Each quest awards 1 Dinar, for a total of 3 Diners at the end of the questline.
The vendors sell trinkets and weapons from their respective raids, and are located to the right of the Great Vault in Oribos. All items cost 1  Puzzling Cartel Dinar each.
The vendors are Ko'ropo (Castle Nathria), Ta'choso (Sanctum of Domination) and So'turu (Sepulcher of the First Ones).
Once you buy 3 items, the vendors leave. You cannot obtain more than 3 items with the Dinar vendors.
This is to help curb the extreme bad luck that players may experience.
Heroic and Mythic gear updates will drop by combining a certain number of shards (currently 20).
Shards have a 100% drop rate and drops from all Fated raid bosses.
These items work on any Fated item, including those bought off the vendors.