For mystics, David Renfield provides bonus but many investigators avoid using him due to doom. Now, Elle helps to solve that problem. With Renfield + Elle, you can get +1 bonus as well as 1 free resource for each round; notice that you do not choose to add doom onto Renfield when triggering his ability.

However, some problems remain. We need Charisma, so that true xp cost of this combo is not 2xp but 5xp (or 7xp for 2 Elle in the deck). In addition, we give up the great ally, Arcane Initiate, or need additional 3xp. Finally, the overall cost of Renfield + Elle is 5 resource, which is high even if we could earn 1 resource per turn. Of course, it is good chance that we revisit David Renfield without any fear about placing a doom.

I write the above review before the least taboo was revealed and now that combo is 13xp. Now, that's too expansive combo IMO.

This card is going to be a staple for doom decks going forward, unless they change something. Elle gives insane value, and for just 2xp. Even if you clear the doom from a card, as long as it is still attached to Elle, you can keep your +1. She plays well with Ghastly Possession and the new Ceremonial Sickle and Dowsing Rod. Together with Sin-Eater, doom will be much easier to manage for any mystic bold enough to play with it.

It only checks 1 or more doom at the moment of attaching/swapping, so if you already managed to get 2 assets attached and then the agenda wipes off all the doom (one doom just does not count towards the threshold, but still in play and to be removed), now you can use clean assets that are already attached which could be handy in agenda with tight doom threshold.