Since Whisper returned, I’ve defaulted back to that. Unless it’s specifically stating an activity or enemy type (a la Skyburner Oath), that’s one of the easier ways to complete catalysts. Endlessly spawning shadow thrall that all funnel into a narrow corridor at the very back of the room. Thrallhalla and the opening of Grasp of Avarice are also decent. Then again, I don’t remember what was involved for Ex Diris’s catalyst, lol.