There are five Malignants Rings that have been added to Diablo 4 after the Season of the Malignant came to an end, which means you can start using some of those powers again. To get the rings though, you need to head back into the dark burrows.
Where to Find Malignant Rings in Diablo 4
You can get the Malignant Rings by defeating the Nightmare Echo of Varshan in the Malignant Burrow or by getting lucky with random drops in Sanctuary. Killing the Nightmare Echo of Varshan on World Tier 3 or World Tier 4 is the most consistent method by a long shot. With the addition of target farming on uniques, each of the Diablo 4 end-game bosses has a list of unique loot that can drop. Varshan has claim over the rings.