Trials of Fortitude quest tutorial video is below. This is the Clerics / Druids quest. Clerics have Mana Shield which have a chance of protecting the Cleric from losing mana or having their SS ability sabotaged. None of my heroes can do either of those things so Mana Shield has no chance of triggering during the quest.
Druids on the other hand have a chance of spawning a minion whenever they are damaged.
In the first level of the quest, I got the Druid to spawn a minion.
Here’s the last level, the hard one. Had to color stack 4 green + Boril. Strategy is to suicide Boss Horghall into Boril’s riposte, then color stack to kill Boril. From there finishing off Vivica is manageable.