Quote Originally Posted by Yencat View Post
I think you can only run the newest MSQ dungeon with Trusts once before they revert back to the actual level you have them at.
Correct. You can run MSQ dungeons once with "scenario mode" trusts (as with the levelling dungeons, it's possible to have "guest star" party members other than the usual party) then it reverts to requiring you to have your trust avatars at Lv80 to replay it.

Getting all avatars to Lv80 does re-unlock scenario mode as well.