Destroyster debuff - non-working mechanics in dimensional rift

It's a mechanic that's still kind of commonly misinterpreted. It works, simply put; the character afflicted from the Destroyster debuff must be killed by an ally before the 3 turns are up. If fulfilled, character is revived with full hp and the debuff is removed.

The double damage from allies the debuff gives helps that part a lot. Not sure how it is for 1-character solo rifts. Hope this helps.

Well you just have to make sure that you don't stand near them when a new wave spawns so they don't curse you immediatly, if you want to play solo

The Sufokia Rift is one of the most difficult rifts to solo due to the potential for a Darth Mussel and highly tanky mobs to appear at the same time. If you can't bring an ally with you, you'll need to play by the rift's rules and prepare for the worst each wave.

When you are down to 1 mob left, don't kill it. Get it as close to 1 HP as you can, then skip the rest of your turn. You can kill it on your next turn, leaving you with a lot of AP/MP to kill the Darth Mussel or position yourself far away. If you can kill it before it has a turn, it can't apply Destroyster. If a Shushu artifact shows up, you can also use that to anchor the Darth Mussel and run away. Remember that Destroyster takes 3 turns to trigger, so it has no effect when applied on the last few waves.

This strategy will give you a lower total waves cleared, since you'll be skipping parts of your turn often. It's a matter of how lucky you feel. I will agree that getting two Darth Mussels at the same time is total diddlydoo though.