Mythic: Uu'nat, Harbinger of the Void

Shadowlands Experience!

This is quite doable with a group of 15+ people, and is likely even doable with 10 or less, if you are willing to put in the time.

You need 2 tanks, 2-3 healers, and as much dps as you can find.

Stay spread out throughout the fight. Rather than trying to group up on the relics with the appropriate people, just stay spread and let the damage hit you. It is a lot of damage but you can survive it. However, if you slam into someone with the wrong debuff, it's an instant kill.

Tanks need to swap still.

Honestly that's about it. This is much, much easier than Mythic Restless Cabal.