For being the Witch of Greed, Echidna sure is helpful and informative! It’s her opinion that there is no limit to how many times Subaru can use Return by Death, as it is limited only by the Witch of Envy’s presently-limited delusion.
Envy wants him to “redo destiny” without mistakes, but doesn’t count, say, what happened to Rem as a mistake. Neither Rem or anyone else are taken into account. Subaru alone is responsible for who is or isn’t lost when the next “save point” is established.
The more immediate concern is, of course, that horde of voracious rabbits, which Echidna identifies as the Great Rabbit. Like the White Whale and Black Serpent, these Three Great Mabeasts were created by Daphne, Witch of Gluttony, over 400 years ago. The Rabbit can only be killed by killing all of its constituent parts simultaneously.
When Subaru requests more info on the Great Rabbit, Echidna arranges for him to meet Daphne one-on-one; such is her ability as the vessel of the souls of all the dead witches. Instead, the childlike Witch of Pride Typhon pops out first, ripping off Subie’s arm and shattering him to bits before the earnest, self-conscious Witch of Wrath Minerva saves him.
After that, Daphne finally appears, bound and chained within a coffin. After questioning why Subaru would destroy the Great Rabbit without first understanding the infinite gluttony that powers it, she offers a useful hint about how to at least get the rabbit where you want it: it is drawn to great sources of mana, like a powerful magic user.
As Subaru exhibits signs he could soon wake up, he beseeches Echidna to tell him how to return to her should he require more of her wisdom. She tells him the conditions for joining her tea party are tougher the more times he’s admitted, but like the last two times, if he needs her, he’ll find a way to get to her, either through the tea party or in the trial itself.
As for the trial: Echidna is losing her patience and interest in Emilia, and is all but convinced the half-elf candidate will never “break out of her shell”, i.e. properly confront her past. Right now she’s much more confident in Subie’s ability to pass. After Echidna receiving payment in the form of the sentiments within the handkerchief Petra gave him, Subie returns to the tomb, his memories of the Witch of Greed fully intact.
The only problem is, Emilia is nowhere to be found. When Subie goes outside, he faces a giant shadow slowly engulfing his surroundings, and Witch of Envy Satella makes her appearance. She draws close to Subie declaring “I love you” over and over and over again.
I’m sure there’s some truth to that, considering the ability she game him. At the same time, as Subie himself is gradually covered in her cloak of darkness, it sure doesn’t look like he should be sticking around, and certainly isn’t going to get anything useful out of her other that “I love you”.
It’s Garfiel (of all people) to the rescue, splitting Subie and Satella up, grabbing Subie and leaping to a (slightly) safer place. There, the two observe Satella not following them, but headed to the barrier. It dawns on Subie: she’s headed for Roswaal’s mansion, and to Frederica, Petra, and the comatose Rem.
Determined not to let Satella “get away with anything else”, Subie no doubt is preparing to chase after her—though I wonder whether Garfiel will be okay with that. After the credits, we see Roswaal in bed about sink under the shadow, and grabs a book (a gospel?) in grim preparation to accompany Subaru in “hell”.
Watching Subaru and Echidna interact is always fascinating, while it was fun to meet three more colorful quirky witches. Interesting too that they’re portrayed as characters with whom Subaru can converse and reason; Satella is much more of an implacable force of nature.
As for the Great Rabbit, I’m sure it can be defeated just as the White Whale was defeated. However, I agree with Daphne: one lone human won’t be enough to do it, which means Subie will have to flex his alliance-building muscles.