The final encounter on the leviathan you fight tje cabal lord himself, calus. During the damage phase of calus, you will see four plates. (Dogs, Sun, Chalice and Axes) In that order. To get the 'question mark' buff you need to use a certain element to each plate For Dogs it is Arc, For sun it is kinetic, For chalice we usually use solar super And axes ia void. Assigning each element to the right plate will givw you the 'question mark' buff Note: When My team plays the leviathan we always start at dogs and move in a counter clockwise direction (Not sure if this method is required to get the buff) Hope it helped