What mechanics could pair up with essence ?

With the possibility to switch between 3 atlas trees I'm trying to experiment things this league. Specifically, I was wondering what could be run in pair with essence farm ?

Correct me if not but essences don't require high tier maps (tier 6 is required now), nor high item rarity/quantity or monster density. I don't think there is any other content with similar conditions, as bossing requires T14+, and most if not all additional content thrives with iiq.
My only guess is Jun missions as the main reward is intelligence, but that's not much, and quite far from essence passives.


So, any idea ?

Enjoy your league start !

harbingers since they don't scale with quant and rarity either.I'm not sure if map tier makes a difference