So I had 2 tasks, both with 1 skull & 1 -Stamina. I was able to complete one of them, but failed the second task. Does my stamina get discarded, or does it go back to my investigator.
Does Stamina automatically get discarded as soon as you choose to use it to try to complete a task, regardless of completing the adventure card?
In this case you would loose 1 Stamina.
To complete the first Task, you rolled the 1 Peril and then discarded a Stamina to complete the Task.
You attempted the second Task but since you didn't roll the required Peril, there would be no need to discard the Stamina.
From the rules, page 6
When all die result requirements for this task have
been met, the active player modifies his Stamina by
the number indicated on the symbol to complete
You only discard Stamina (or Sanity or Advance the Clock) once you have meet all the dice requirements. If you don't meet the dice requirements, then you don't discard the Stamina.