This post I authored months ago questions the use of the term "toughness". I recently found a reference in the Strange Remnants expansion that states:
If the active Mystery requires an Epic Monster to be defeated, place two Health on the card. The Epic Monster's toughness is reduced by one for each Health on the active Mystery.
The act of placing health markers strongly implies to me that it is to be treated as if one did 2 damage on the monster, yet the wording here clearly states that the markers reduce the toughness of the monster and do not necessarily do damage. This makes me question whether my original post regarding whether toughness was a measure of max or current HP was concluded incorrectly. The only way it could be valid is if this treatment of Epic Monsters when advancing mysteries is explicitly different from the normal course of doing damage to monsters, which seems less likely, given that I haven't found any actual supporting documentation that clarifies that toughness is max HP. Thoughts?