Was just playing the new delve when I saw Tartarus flashing “Darken souls” on my turn. The text of the trait says “gain an extra soul when matching purple gems” but whenever anyone on either side makes any color match, it will still flash as though it has been activated. I haven’t been able to actually pull one yet so I can’t test it in play to see if it’s mechanical as well as visual as I forgot the delve weekend was coming and spent all my shards a couple days ago like a smart boy.
Edit: Platform is mobile, Galaxy s9, and it has happened multiple times when I’ve made it to the final room of the delve. Delve event, not daily delve if that makes any difference. I wasn’t paying attention during the quest fights to see if it happened there as well and since they’re complete I can’t replay them.