2020-08-07 : If a nontoken creature dies at the same time as Ulvenwald Mysteries, the first ability triggers.

2020-08-07 : If you sacrifice a Clue as part of casting a spell or activating an ability, the last ability will resolve before that spell or ability.

2020-08-07 : The last ability is a triggered ability, not an activated ability. It doesn't allow you to sacrifice a Clue whenever you want; rather, you need some other way of sacrificing it, such as the activated ability that Clue tokens have.