Satella - Re:Zero
Name: Satella
Age: Unknown
Race: Half Elf
Gender: Female
Birthday: Unknown
Voice Actors: Takahashi Rie (Japanese)
Satella is also known as the Witch of Envy and is one of the Witches of Sin. She is a half elf who has a thing body with long silver hair, and blue-purple eyes. Emilia looks exactly like her. During a brief encounter with Subaru in Echidna's tea party, she wore a dress comprised of black shadows that resonated with her heartbeat.
History
Contrary to the fairy tales and history books written on her, Satella and the being known as the Witch of Envy are actually separate personalities. 400 years or so prior to the start of the story, Satella the half elf absorbed the Witch Factors of Envy that she had no compatibility with. This resulted in the creation of the Witch of Envy personality. She ended up going out of control, killed six other Witches of Sin, and nearly destoyed the world. The exact details of this event are still unclear, but according to those witches via Echidna's powers it was not the Witch of Envy who was responsible for that, but rather Satella herself.
Regardless, this caused some of the most powerful individuals of the time to band together to contain the threat. The Dragon Volcanica, the Sword Saint (of the time) Reid Astrea, and the sage Flugel (though his name was stripped from the history books) combined their might but were still unable to fully kill her. Instead, Satella was sealed in a shrine. Although Arc 6 is not yet complete and most of it is non-canonically documented in the web novel, there are rumours that at least some aspect of Satella is contained beneath the Pleiades Watchtower.
In fact, according to Echidna a number of failsafes were put in place including the sealing of Echidna herself to the Witch of Greed's Graveyard in her Sanctuary. She says that it was planned by Volcanica himself since the seals were not guaranteed to hold forever. In fact even with all of the seals being intact, The Witch of Envy has already exerted her power and will outside of her prison on multiple occassions.
The first notable feat is pulling Subaru to the world. Every time he Returns by Death he visits a strange limbo where he sees visions of Satella. These short visits have been growing in intensity every time he dies. The Witch (though it is not entirely clear which personality is in full control through the seals) also exerts power over him and threatens to kill him or the people around him if he reveals his ability. Her power manifests for him as a slowing of time where he can feel her shadowy hands clutch his heart and threaten to crush it. Pushing past that fear, she has also killed others (such as Emilia in one loop) if he keeps revealing his Return by Death ability. She also completely rejected Petelgeuse when he attempted to possess Subaru, stating that Petelgeuse wasn't the one she loved.
Subaru meets an aspect of Satella in Arc 4 when he visits Echidna for a tea party and chat. After overcoming his own mental blocks, he admits that she looks exactly like Emilia. In one timeline during the events at the Sanctuary, Emilia is possessed by the Witch despite her seals seeming to still be in full force. While it has been hinted that there is a strong connection between Emilia and Satella, nothing has been confirmed as of yet. Satella and the Witch of Envy act as a very strong force behind the scenes that drive the mystery of Re:Zero.
Relationships
Echidna - Echidna the Witch of Greed has what seems to be Satella's soul (in addition to the five other Witches of Sin consumed by Satella). Satella has materialized herself in Echidna's reality on numerous occassions.
Natsuki Subaru - Satella has professed her love for Subaru on multiple times. In fact both the Satella and Witch of Envy personalities are in love with him, though there is still no known reason why. In a moment of lucidity via Echidna's powers Satella begs Subaru to just kill her, but Subaru proclaims that he will save her instead.
Emilia - Emilia struggled most of her life with looking like the description of the Witch of Envy from legend, but it is hinted that they do in fact share some sort of connection. Not much concrete has been revealed yet, but Satella was once able to possess Emilia and she has been referred to as a potential vessel for Satella on multiple occassions.
Abilities
Due to most of her existence being clouded in mystery, Satella's full abilities are still kept a secret. However, she has been documented to have these following abilities:
Authority of Envy - The full abilities of this are not yet revealed though there is speculation that is affects a target remotely.
Authority of Sloth - Satella uses the Unseen Hand technique to threaten Subaru whenever he mentions his Return by Death ability.
Shadow Control - Satella exerts control over shadows around her, though it is unknown if it is tied into her Authority or even some other ability altogether. These shadows are able to destroy life and even take abstract concepts like thoughts and memories (thus bearing some resemblance to the Authority of Gluttony).
Time Manipulation - Time seems to stop for Subaru every time he is threatened by the Witch of Envy.