Jewelry is hard to come by in Diablo 4. Hence, if you do manage to find a good unique ring, hold on to it and spend money to upgrade the ring because you are not going to come by a better one for a while.
To further prove that point, there are only four unique rings in Diablo 4, one of which is a guaranteed drop and two of which are non-class exclusives.
Hunter’s Zenith (Druid)
Hunter’s Zenith is a Druid-exclusive unique ring and a mighty powerful one at that in Diablo 4.
That being said, the most use you are going to get out of this unique item is if you are making a hybrid Druid build, meaning that you are going to be using both Werebear and Werewolf skills.
Its unique effect gives you a bonus depending on your next shapeshifting. Transforming from a Werebear to Werewolf is going to make your next non-ultimate Wereskill free while going from Werewolf to Werebear is going to make your next Werewolf skill give you a massive heal.
Furthermore, Hunter’s Zenith increases the damage dealt while shapeshifting. This means that your Pulverize skills, for example, where you shapeshift is going to a ton more damage.
Other modifiers increase your critical strike damage with Werewolf skills and overpower damage with Werebear skills.
As already stated above, you need to be spending your skill points in both shapeshifting skills, or else the Hunter’s Zenith is going to be of little use to you in Diablo 4.
Mother’s Embrace (General)
You get Mother’s Embrace by defeating Lilith, the final D4 boss. The unique ring refunds a good amount of resources if you land your core skill on five or more enemies in back-to-back succession.
This should not be a problem while running dungeons, making this an overpowered unique item to have on AOE builds.
Furthermore, Mother’s Embrace increases your critical strike damage and overpower damage as well. All of your stats get a further boost based on the affix you get with the item alongside a good amount of resistance against fire and shadow damage.
Ring of Mendeln (Necromancer)
The Ring of Mendeln is unique and it is specifically for the necromancer class. When you have at least 7 minions with you, there will be a 10% chance that the minions will deal explosive damage which will deal heavy physical damage to enemies.
The Ring of Mendeln also provides cold and shadow protection. You will also get an increase in Lucky Hit chance, an increase in Minion attack speed an increase in minions’ maximum health, and a decent amount of thrones.
The Ring of Mendeln is a random drop and you will need to fight monsters, open chests and break objects to find the ring.
Ring of Starless Skies (General)
Ring of Starless Skies is another non-class unique ring to find in Diablo 4. This is important because finding good unique rings is hard as it is in the game.
Ring of Starless Skies reduces the cost of your next core skill by nearly half (depending on the affix) while using your core skills. Yes, all you have to do is continue using your core skill to increase the chance of cost reduction on each cast.
The rest of the modifiers increase your core skill damage, critical strike chance and damage; all the more pushing you to spam your core skills as much as possible.